ML18227E210

Submits Baseline Ecological Study of a Subtropical Terrestrial Biome in Southern Dade County, Floroda.

ML18227E210
Person / Time
Site:	Turkey Point
Issue date:	01/31/1978
From:	Applied Biology
To:	Florida Power & Light Co, Office of Nuclear Reactor Regulation
References
Download: ML18227E210 (396)

Text

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moLfI 'L'ILG BASELINE ECOLOGICAL STUDY OF A SUBTROPICAL TERRESTRIAL BIOME IN.SOUTHERN DADE COUNTY, FLORIDA Docket 0 CmIrglm g

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~>IF~cDQ F,:)!.'.m'R'OYCacumenh 0'"GCUYCGY 00 CIIET FILE jANUARY 1978 APPLIED BIOLOGY, INC.

Ecological Consultants 8

641 DeKALB INDUSTRIALWAY ATLANTA,GEORGIA 30033 TELEPHONE (404) 296-3900

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AB-97 BASELINE ECOLOG I CAL STUDY OF A SUBTROP I CAL TERRESTRIAL BIONE IN SOUTHERN DADE COUNTY, FLORIDA Prepared for FLORXDA PONER 6 LIGHT COMPANY MIAMI, FLORIDA By APPLIED BXOLOGY, INC.

ATLANTA, GEORGIA January l978

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CONTENTS Pa<ac

1.0 INTRODUCTION

- 1-1 1.1 Background Information 1-1 1.2 Description of the Region 1-4 1.3 Study Rationale 1-5

1. 4 Summa ry 1-9 1.4.1 Natural Plant Associ ations 1-9 1.4.2 Soil Analyses and Characteristics - -- -- 1-10 1.4.3 Kinds and Abundance of Native Animals --- 1-11 1.4.4 Experimental Studies- 1-13 2.0 DEFINITION OF TYPES AND RELATIVE ABUNDANCE OF OF NATURAL PLANT ASSOCIATIONS 2-1 2.1 Introduction 2-1 2.2 Natural Plant Associations 2-4 2.2.1 Fringe Forest 2-4 2.2.2 Dwarf Mangrove 2-4 2.2.3 Black Rush/Salt Grass 2-5 2.2.4 Saw Grass 2-5 2.2.5 Hammocks- 2-9 2.3 Soil Analyses and Characteristics 2-15 2.3.1 Major Soil. Types 2-15 Miami Oolite 2-15 Naris 2-15 Peats 2-16 2.3.2 Soil Characteristics 2-18 Soil Sampling Station;Locations (for Stratigraphy, Bulk Density, Carbon and Carbonate, and Salinity Studies)---- 2-18 Soil Stratigraphy 2-18 Methods 2-18 Results- 1 2-19 Bulk Density 2-23 Methods 2-23 Results 2-23 Carbon and Carbonate Analyses --- -- -- 2-25 Methods 2-25 Results 2-25 Soil Salinity 2-26 Methods 2-28 Results 2-28 Soil Sampling Station Locations (for ATP, Soil Moisture, pH, and Organic and Inorganic Carbon Studies 2-32 ATP 2-33 Soil Moisture 2-37 S oil pH 2-38 Organic and Inorganic Carbon ---- -- -- 2-38 11

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CONTENTS (continued)

~Pa e 2.3.3 Soil Microbiology 2-43 Methods 2-43 Results 2-44 Numbers of Bacteria in Soi 1--- 2-44 Taxonomy of Soil Bacteria----- 2-46 Physiological and Metabolic Characteristics 2-46 Carbon Metabolism 2-49 Nitrogen Metabolism 2-49 2.3.4 Soil Profile 2-52 Introduction 2-52 Methods 2-53 Hammock Soil Transects --------- 2-53 Subsurface Stratigraphy --- ----- 2-53 Results 2-56 2.4 Summary 2-58 3.0 KINDS AND ABUNDANCE OF NATIVE ANIMALS 3-1 3.1 Introducti on 3-1 3.2 Birds 3-5 3.3 Mammals 3-15 3.4 Reptiles and Amphibians 3-18 3.5 Fish 3-23 3.6 Selected Invertebrates 3-27 3.6.1 Soil Macroinvertebrates 3-27 3.6.2 Surface and Arboreal Molluscs 3-27 3.6.3 Insects and Spiders 3-30 3.6.4 Zooplankton 3-42 3.6.5 Aquatic Molluscs 3-45 3.7 Su'mmary 3-49

4. 0 EXPERIMENTAL STUDIES 4-1 4.1 Introduction 4-1 4.2 Vegetation Peak Standing Crops 4-2 4.2.1 Methods 4-2 4.2.2 Results 4-3 Species Density and Areal Coverage- 4-3 Vegetative Biomass - 4-7 4.3 Effects of Soil Characteristics on Plant .

Association Groups 4-21 4.3.1 Introduction 4-21 4.3.2 South Dade Soils 4-21 4.3.3 Distribution of Hammocks 4-22 4.3.4 Distribution of Mangroves 4-23 4.4 Nutrient Turnover in Salt Marshes 4-24 4;4.1 Introduction 4-24 111

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CONTENTS (continued)

~Pa e 4.4.2 Hydraulic Studies 4-24 Methods 4-24 Results 4-26 4.4.'3 Nutrient Determination in Mangrove Soils 4-29 Nitrogen 4-29 Phosphorus 4-31 Micronutrients 4-36 Nitrogen Fixation 4-39 4.4.4 Organic Carbon Productivity ---- ------- 4-43 Productivity of Trees and Grasses ------- 4-44 Methods 4-44 Results 4-44 Productivity of Phytoplankton and Benthic Algae 4-46 Methods 4-46 Results 4-46 4.4.5 Mangrove Contribution to Adjacent Estuary 4-47 Methods 4-47 Results 4-51 4.5 Effects of Groundwater Seepage on Mangroves ---- 4-58 4.5.1 Distribution of Vegetation 4-58 4.6 Summary 4-60 LITERATURE CITED 4-63

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LIST OF FIGURES Figure ~Pa e Location of South Dade Site 1-3 2-1 Distribution of major vegetation zones at the South Dade study area- 2-3 2-2 South Dade Area dwarf mangrove zone vegetation inventory 2-6 2-3 South Dade Area black rush/salt grass zone vegetation inventory 2-7 South Dade Area saw grass zone vegetation inventory 2-8 2-5 South Dade Area saltwater hammock vegetation

'inventory 2-11 2-6 South Dade Area brackish water hammock vegetation inventory 2-12 2-7 Bright band of calcitic mud deposition parallel to shoreline, and study transect station locations 2-17 2-8 So i 1 strati graphy at 17 s tat i ons in di ffere n t vegetation zones 2-20 2-9 Salinity and chlorinity values along study transect 2-30 2-10 Depth profiles by stations and parameters----- 2-39 2-11 Location of study hammock in dwarf mangrove zone 2-54 2-12 Hamock study transects 2-55 3-1 Outflight patterns from West Arsenicker Key rookeries, Hay 1977 3-14 3-2 Diversity of day insect collections (mean, range and standard error), South Dade Area---- 3-40 4-1 Study transect station locations -----;------ 4-4 4-2 Distribution and biomass of dwarf mangrove zone by component and species 4-8 4-3 Leaf biomass and leaf area in the dwarf mangrove zones 4-9 4-4 Distribution of biomass in black rush/salt grass zone by component and species -- ------- 4-11

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LIST OF FIGURES (continued)

~Fi ures ~Pa e Leaf biomass and leaf area in black rush/

salt grass zone 4-12 4-6 Distribution of biomass in black rush/salt grass zone by component and species ------------ 4-13 4-7 Leaf biomass and leaf area in black rush/

salt grass zone (off transect) 4-14 4-8 Distribution of biomass in saw grass zone by component and species 4-17 4-9 Leaf biomass and leaf area in the saw grass zone 4-18 Approximate locations of fresh and sal t water interface, August 1974 4-25 4-11 Nitrogen fixation in grams of ni trogen per gram of sediment per year 4-40 4-12 Nitrogen fixation in grams of nitrogen per gram of algal mat per year 4-41

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LIST OF TABLES Table ~Pa e Major contributors of South Dade Area research material 1-8 2-1 Vegetation zone acreage of South Dade Site ----- 2-14 2-2 Bulk density measurements for South Dade Area soils 2-24 2-3 Average calcium, magnesium and strontium composition of the carbonate fraction of marls and peats along the South Dade study transect--

2-4 Salinity in parts per thousand (%, ) from ground water of major vegetation areas --- --

2-5 Adenosine triphosphate (ATP) in soil samples from non-hammock areas near Stations 2, 18, and 30 2-35 2-6 Adenosine triphosphate in soil from 'drainage 2, 18, and 30 tail'f (ATP) hammocks samples near Stations 2-36 2-7 Depth analysis of organic and inorganic carbon content of soil 2-41 2-8 Derived counts of colony-forming units (CFU) of aerobic and facultative anaerobic bacteria ----- 2-45 2-9 Cluster analysis of soil isolates showing groups with > 80% coefficients of association -- 2-47 2-10 Summary of hydrolysis of various substrates by, all isolates in a soil column, Stations 2, 18 and 30 2-50 3-1 Status category definitions extracted from the inventory of rare and endangered biota in Florida 3-3 3-2 Birds found within or near the South Dade Site (not on r.are or endangered list) -------- 3-6 3-3 Rare or endangered birds found within or near the South Dade Site 3-10 3-4 Mammals collected or sighted in the South Dade Si te and vi cini ty 3-16 3-5 Reptiles and amphibians observed within the South Dade Site 3-19

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LIST OF TABLES continued Table ~Pa e 3-6 Reptiles sighted outside of South Dade Site ---- 3-20 3-7 Fishes collected and observed at the South Dade Area 3-24 3-8 Soil macroinvertebrates collected at the South Dade Area 3-28 3-9 Surface and arboreal molluscs collected at the South Dade Area 3-29 3-10 Insects collected in the South Dade Area ------- 3-31 3-11 Zooplankton groups collected at South Dade Area and their relative abundance by habitat --- 3-44 3-12 Aquatic molluscs collected within the South Dade Area 4-1 Vegetation type and areal coverage of major zones of the South Dade Site 4-5 4-2 Density of mangrove species (individuals/mz) along the South Dade study transect --- ------- 4-6 4-3 Biomass estimate of 424.4 hectares of black rush on the South Dade Area Total biomass of saw grass on the South Dade Area 4-19 4-5 Distribution of biomass (g/mz) in the various vegetative zones on the South Dade Area exclusive of hammock biomass 4-20 4-6 Total Kjeldahl nitrogen in south Dade soils during November 4-30 4-7 Inorganic phosphorus analyses of south Dade soils during the winter (November) ----------- 4-32 4-8 Inorganic phosphorus analyses of south Dade soils during spring (February) 4-34 4-9 Inorganic, organic, total and percent of total phosphorus values of south Dade soils -- ------ 4-37 4-10 Magnesium, manganese, potassium, strontium, and zinc analyses of south Dade soils ---------- 4-38

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LIST OF TABLES continued Tabl e ~Pa e 4-11 Mean concentrations of particulate detrital material in the tidal waters 4-52 4-12 Amounts of total, inorganic, and organic dissolved carbon in the tidal waters during November 4-54 4-13 Measured transport of detrital organic matter dpring January, February, October and November 1976 4-55 4-14 Elemental composition of detritus after 70 days of decomposition - - --- - -- 57 4-15 "

Summaries of the respiration and production values by vegetative zone 4-62

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1.1 BACKGROUND

INFORMATION This document has been prepared in response to Operating License Nos. DPR-31 and DPR-41, Section 4.0-8-1, a, b, and c of the Technical Specifications prepared by the Nuclear Regulatory Commis-sion (NRC) for Florida Power & Light Company's (FPL) Turkey Point Units 3 and 4. The specifications are as follows:

a. Definition of different types and relative abundance of natural plant association as a function of topography over a 10,000-acre tract [actually about 10,500 acresj that includes tidal, mangrove salt marsh, fresh-water wetlands, and dry land communities.

This will include analyses of the character-istics of the soils in which these plants are formed (e.g., depth of organic layer, pH, available nutrients, soil profile, salinity, etc.) as a basis for predicting conditions under which these plant associa-tions will survive.

b. Study the kinds and abundance of native animals that live in association with the different plant communities and utilize them for food and shelter and breeding.

In this phase of the study, field observa-tions and trapping techniques will be used to prepare accurate lists of the species noted, especially any rare or endangered species, and will include birds, mammals, amphibians, reptiles, fishes and selected invertebrates.

c. Experimental studies on selected parameters such as:

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(a) peak standing crop of different plant species as a function of seasons of the year, (b) effects of certain soil characteristics on occurrence of plant association groups, (c) nutrient turnover in the mangrove salt marsh and its relative contribution to the adjacent estuary areas, and (d) effects of possible ground water seepage on mangrove ecosystems.

NRC further stated that "... an intensive and comprehensive three-year program would be undertaken to establish baseline ecolog-ical conditions and characterize the flora and fauna of a tract of land that was ecologically similar to the Turkey Point Site." FPL complied by starting a program in 1973 which responded to all of the environmental parameters in the Appendix B Technical Specifications.

There were valid reasons for not conducting a baseline program on the Turkey Point Site itself. Construction of the canal cooling system was started prior to finalization of the proposed ecological programs, and it would have been scientifically unsound to study a 1

habitat undergoing modification. Also, from a purely practical standpoint, environmental surveys would have been difficult to conduct amid heavy drag line and earth-moving equipment.

A habitat ecologically similar to the Turkey Point Site was available for study in southern Dade County. This 4252-hectare (10,500-acre) site, designated as the South Dade Site, was already owned by FPL (Figure l-l) and shared a cordon boundary 1-2

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with the Turkey Point Site. Therefore, biological data from the South Dade Site were evaluated to assess the impact of the construc-tion of the closed-loop cooling canal system on the Turkey Point Site.

1.2 DESCRIPTION

OF THE REGION Both the Turkey Point canal system and the immediately adjacent South Dade Site lie to the west and south of Card Sound and Little Card Sound (hereafter referred to as Card Sound for brevity). These two small water bodies are contiguous with the southern reaches of Biscayne Bay.

The region is subject to heavy periodic inundation by rainfall, about 127 to 152 centimeters (50 to 60 inches) per year. The volume of runoff resulting from a rainfall depends on the groundwater le'vel at the time of the rainfall. During the dry season when groundwater levels are low, the aquifer will hold additional water, so, infiltra-tion of surface water is greater and runoff is small. During the wet season when groundwater levels are near the ground surface, the aquifer has little capacity to store water, and the amount of infil-tration is small. Runoff is inhibited during the wet season, however, due to increased tidal levels in Card Sound. As a result, much of the site is covered with standing water during the wet season that is continuous with tidal waters (Dames & Hoore, 1976).

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The topography of the land is low and flat, thus rainfall drainage is slow. The slight downward slope of the land, about 1.8 centimeters per 100 meters, keeps the inland regions draining into Card Sound. The construction of the Model Land Canal and the South Florida Water Management District's borrow canal and Levee 31-E have interrupted fresher water sheet flow and directed surface water flow away from the study areas.

1. 3 STUDY RATIONALE Mangroves and saltwater wetlands are believed to be vital to the well-being of nearshore and offshore fisheries. The coastal fringes of the South Dade Site and the Turkey Point Site support mangroves and saltwater wetlands, which lie further inland and blend into freshwater plant communities. What effects, if any, will the presence of the Turkey Point canals have on the mangroves and adjacent Card Sound?

Without proper baseline data, statements about environmental effects of the Turkey Point canal system would be pure conjecture.

Complex questions needed to be answered, such as how productive are these associations and what are the physical parameters that control them? What are the native animals of the area and how do they rely on the vegetation? How will the presence of canals, buildings, and roadways directly a'djacent to this coastal zone affect this productivity?

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Answers to these and other related questions were not forth-coming from published scientific literature, for enormous gaps existed in many technical aspects of estuarine and terrestrial ecology. Salt marshes and coastal zones had received little scientific scrutiny un-til the past several decades, when the role played by coastal zones was recognized as being crucial to the cycling of nutrients into the marine food chains. Therefore, explanation of the complex biochemi-cal and thermodynamic (energy-flow) networks are scarcely given by present-day science and technology. Basic research was needed to identify the complex life systems which interact in the zones where the land meets the sea. Accordingly, teams of researchers from three universities and several consulting firms were engaged by FPL to con-duct field and laboratory studies which would identify and describe the biological, biochemical and microbial activity of the South Dade habitat. With these data, reasonable estimations might be made which would apply to the habitat at the Turkey Point Site.

To study in depth each of the 4252 hectares (10,500 acres) present in the South Dade Site was not practical. Therefore, as in other ecological baseline studies of this magnitude, the scientific efforts were focused upon the habitats that were most representative of those found throughout the South Dade Site. In the opinion of the scientific community, the most critical habitats from an ecological standpoint were located in the transition between the upland saw grass prairies and the marine waters of Card Sound. Accordingly, a measured 1-6

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transect of land 100 meters (330 ft) wide was established which extended from a point just south of the Sea Dade Canal to a nearshore point in Card Sound. The transect extended sufficiently far inland to include most major habitats found within the South Dade Site boundary and representative of conditions at Turkey Point. In some instances it was necessary to locate research projects away from the transect to serve as a control or when destructive sampling of vege-tation was required. Although the study was most intense in and around the transect, it was not limited to the transect. The area encompassed by the Model Land Canal, the Sea Dade Canal, Canal and Levee 31-E, and Old Dixie Highway, known as the South Dade Area, was evaluated in detail for its flora and fauna.

Over 70 scientists and .technicians from three univerisities were engaged between 1973 and 1976. These research teams, identified in Table l-l, conducted field and laboratory studies which would iden-tify and describe the biological, biochemical, and microbial acti vity of the South Dade Area. Other subcontractors also provided environ-mental data during the study period.

Thi,s report is a summary of the three-year program that was con-ducted in coastal salt marsh and saw grass ecology of the South Dade Area. In order to facilitate readability, only a fraction of the tabu-lar, graphic, and mathematical data has been included in this report. *

• See Literature Cited, page 4-61 and 4-62.

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TABLE l-l MAJOR CONTRIBUTORS OF SOUTH DADE AREA RESEARCH MATERIAL Major Contributors Ma 'or Stud Area Reference Samuel C. Snedaker Natural plant associations and Ecological studies on a subtrop Rosenstiel School of Marine soil characteri s ti cs. ical terrestrial biome. Final and Atmospheric Sciences report. Prepared for Florida 4600 Rickenbacker Causeway Power & Light Co., Miami, Florida.

Miami, Florida Connell, Metcalf & Eddy Kinds and abundance of native Biological data collected for PPL Engineering and Environ animals. for this report only.

mental Consultants Miami, Florida Dames & Moore Surface water hydrology. Surface water investigations, South Consul tants in Environmental Dade biological study, South Dade and Applied Earth Sciences Area. Prepared for Florida Power &

Boca Raton, Florida Light Co., Miami, Florida Jack H. Fell Vegetative litterfall, micro- The role of microorganisms as indi-Rosenstiel School of Marine biology, nutrient turnover in cators of changing environmental con-and Atmospheric Sciences salt marshes. ditions in mangrove and marsh commun-4600 Rickenbacker Causeway ities. A final report (Section A) on Miami, Florida a research project in South Dade County'submitted to Florida Power 8 Light Co., Miami, Florida Edward L. Fincher Microbiology, organic and Ecological stodies of a subtropical School of Biology inorganic carbon content of terrestrial .biome: microbial ecology.

Georgia Institute of soils. Summary report, March 1, 1976-August Technology 31, 1976. Project No. G 32-630.

Atlanta, Georgia Prepared for Florida Power & Light Co.,

Miami, Florida.

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1. 4

SUMMARY

The intent of this report is to establish baseline ecological conditions of habitats similar to Turkey Point. The parameters studied in-depth were natural plant associations, soil analysis and characteristics and kinds and abundance of native animals. Additional experimental studies were conducted on surface water hydrology, nutrient turnover and microbiology of salt marshes, and nutrient con-tribution to adjacent Card Sound.

1.4.1 Natural Plant Associations Natural plant associations (Section 2.2) were strongly influ-enced by two major determinants: tolerance to water of varying chloride (salt) concentrations and the distribution of high organic-containing soils, mostly mangrove peats.. Zones of vegetation were delineated and maintained based upon a plant species being able to withstand physio-logical stresses imposed by salt-induced osmotic pressure. Density and acreage of plant species were identified and described using prin-cipal vegetative characteristics, as follows:

a. Frin e forest - comprised of large red mangroves forming a ense fringe bordering the coast

b. Dwarf man rove - a population of stunted or diminutive red, lac , or white mangroves which are not believed to be a dwarf race or variety, but rather have dwarf characteris-tics imposed by the high chloride concentrations and low phosphorus content of the soils

c. Black rush salt rass - two grass-like species which occur etween t e more sa >ne soils of the dwarf mangroves and

.the fresher water saw grass habitat 1-9

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d. Saw rass - generally in fresher. water and about one mile in and from Card Sound waters

e. Salt water hammocks - slightly elevated oval or round masses of rich organic peat which support dense stands of mangroves

f. Brackish water haomocks - with configuration similar to salt water hammoc s except that a different plant species composition occurs.

1.4.2 Soil Anal ses and Characteristics The South Dade Site soils (Section 2.3) are comprised of non-stratified calcitic mud which is lai gely finely-divided calcium and magnesium carbonates. Soil depth to bedrock varies from 1.2 meters (4 ft) to occasional out-croppings which broach the surface of the soil. Scattered randomly within the calcitic mud are pockets or lenses of organic peat. These are comprised of mostly dead roots and other degraded plant products. Peats may or may not broach the surface.

Peat deposits which do broach the surface may characteristically support dense mangrove-dominated vegetation to form salt water or brackish water hammocks. Red mangrove peats spaced between layers of calcitic mud strongly suggests the region has fluctuated between marine and freshwater influences during its geological past. The freshwater calcareous mud was probably the earliest sediment type formed on this coast. At some later time, mangroves began to colonize the calcareous mud areas.

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I 1.4.3 Kinds and Abundance of Native Animals Studies were conducted to determine the kinds and abundance of birds, mammals, reptiles, amphibians, fish, arboreal and aquatic molluscs, insects, spiders, and soil macroinvertebrates (Section 3.0).

Animal species observed at the South Dade Site were researched to determine their status with respect to the U.S. Department of the Interior's endangered and threatened wildlife lists, the State of Florida Game and Fresh Hater Fish Commission wildlife code, and the Florida Committee on Rare and Endangered Plants and Animals inventory of rare and endangered biota of Florida.

The South Dade Site is unattractive to the large wading birds as a rookery or nesting area. These species prefer the security of small islands and densely wooded areas with tall trees which provide a measure of protection against predators. The Arsenicker Keys and Mangrove Key, small mangrove-covered islands lying about 3 kilometers (1.8 miles) east of the Turkey Point cooling canals, provides the requisite isolation for the location of rookeries. An estimated 4,000 wading birds have been observed in these small islands. Ten percent or less of this population use the South Dade Site as a forage area.

Among the aquatic birds the most common birds observed along the coast were, in decreasing order, the little blue heron, white ibis, great egret and snowy egret.

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Only five species of mammals were sampled during the study and five other species observed. Sampled species were the rice rat, cotton rat, raccoon, black rat and house mouse. Observed species included the white-tailed deer, marsh rabbits, bobcat, manatee and bottle-nosed dol-phin; the latter two aquatic mammals occurring in South Florida Water Man-agement District canals and offshore, respectively.

Reptiles observed within the South Dade Site were anoles, water snakes, indigo snakes, racers and rattlesnakes. Amphibians were represented by cricket frogs, greenhouse frogs, pig and leopard frogs and various tree-frogs. No alligators or crocodiles were observed on the site; however, these species were seen within the adjacent cooling canal system, Intercep-tor Ditch and Canal, and Levee 31-E. It is possible that small numbers of alligators may occur almost anywhere on FPL property. Crocodiles seem to be attracted to man-made canals and borrow pits because they prefer deep, quiet-water sites.

Twenty-four species of fish'ere collected at the South Dade Area.

With the exception of scattered ponds, the inland areas are usually dry.

During the wet season, especially September through November, the inland areas may support relatively large populations of fish. The species most coranonly collected included mosquitofish, killifish, silversides and mo-jarras. These species provide forage for wading birds and larger carnivor-ous fishes. No species of fish currently listed as threatened or endan-gered on federeal or state lists are known to occur within the South Dade Si te.

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1.4.4 Ex erimental Studies Experimental studies (Section 4.0) were conducted in the South Dade Area to determine peak standing crops, the effects of soil char-acteristics on plants, nutrient turnover in salt marshes, and possible influences of groundwater seepage on mangroves. Within the mangrove zones, red mangroves comprised over 78Ã of the total above-ground biomass. Leaf biomass was found to be 139 g/mz and leaf area was 0.2 mz/m2. Values for black rush/salt grass and saw grass zones were also calculated. Detritus accumulation, leaf biomass, and leaf area were found to increase as a function of distance from the shoreline.

Soil characteristics were found to play a minor role in nutrient cycling. The distribution and sources of water played a more signifi-cant role in determining plant distribution. The majority of the plant coranunities were found on inorganic calcitic substrates. The calcitic soils at the South Dade Site are relatively infertile due to the dominance of calcium and magnesium carbonates and only minimal amounts of other requisite elements. Mangrove distribution was not found to depend upon specific soil types, but rather on the relative position to the shoreline of Card Sound and tidal influences, Tidal flow and amplitude studies determined that the horizontal distance traveled by the landward edge of the water during the dry season did not extend more than 700 meters from the shoreline. During the wet season, standi ng freshwater from rainfall was continuous with 1-13

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Card Sound water. Normal tidal motion was imparted, and tidal effects were therefore observed throughout the study area. Tidal movements and storms are believed to be the mechanisms that release and transport nutrients from the black rush/salt grass and saw grass zones to Card Sound.

The detrital export dynamics of the South Dade Site were evaluated in relation to actual litterfall, the decomposition rate, and the amount of litter remaining on the surface. The majority of the detrital export was in the form of small particles between 0.45 and 62.0pm in size. Organic matter may be either exported to or imported from Card Sound; that is, particulate matter may leave the system and enter Card, Sound or be transported from Card Sound into the South Dade Site habitats..

The effects of groundwater seepage on mangroves were deter-mined. Different mangrove species respond in various ways .when exposed to varying saline regimes. Exposure to increasingly fresh water likewise was shown to have a profound effect upon the distri-bution of mangrove species. The presence of mangrove species in higher saline habitats reflects the inability of other species to cope with physiological stresses induced by salts. Therefore, in-creased seepage of saltwater at concentrations near that of seawater in the South Dade Site soils could be expected to favor the growth of mangrove:species at the expense of the less salt-tolerant vegetative species.

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2.0 DEFINITION OF TYPES AND RELATIVE ABUNDANCE OF NATURAL PLANT ASSOCIATIONS"

2. 1 INTRODUCTION The first part of this section discusses the different types and relative abundance of natural plant associations found in the South Dade Area. The various plant associations that comprise the mangrove salt marshes, wetlands and dry land communities are defined.

The second part of this section investigates how these plant associa-tions relate to the topography and soil characteristics of the study area as a basis for predicting conditions under which plant associa-tions will survive.

The vegetative characteristics of the South Dade Area change from northwest to southeast. Plant communities differ dramatically as a result of slight variations in topography which affect the tidal intrusion of saline waters from adjacent Card Sound. Dense mangroves flourish along the coast. This mangrove community recedes into salt-tolerant grasses, that, in turn, blend into freshwater dominanted by saw grass. Throughout these vegetation zones are hammocks, or tree islands, so named for their appearance as islands protruding above the expanse of grasses upon a flat plain. Viewed from low-flying air-craft, these teardrop or circular-shaped islands appear to punctuate the fields of saw grass and rushes below. Hammocks are rich with peat and other accumulations of organic matter that support heavy 2-1

vegetative growth. The geological origins of these rich organic deposits have not been identified.

The major natural plant associations found in the South Dade Area are fringe forest (comprised of mangroves}, dwarf .

mangrove, black rush/salt grass, saw grass, and hammocks (Figure 2-1).

The fringe forest and dwarf mangrove zones are part of the mangrove salt marshes. The black rush and salt grass zone is also predominately a saltwater association, but the upland portions of this zone merge into the wetlands of the saw grass zone. Hammocks are the only dry land community during the summer wet season, but during the dry winter season the saw grass and black rush/salt grass zones are also essentially dry -land habitats.

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Fi (FW Distr'1bu GIagor vegetation zones af the de Study Area. Photo data taken in 1964. ~ o/e.l-0 r ,1 "F 4 fig Sca fe. 1;, cm = 266 v,:

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2. 2 NATURAL PLANT ASSOCIATIONS 2.2.1 ~Fi The shoreline of the South Dade study area is a fringe forest of mangroves. The fringe forest does not extend sufficiently inland to allow for species zonation but is composed solelv of the red mangrove, Bhisopho~a mangle. The red mangrove coranunity is best developed along shorelines with elevations above the mean tide line. The proproot system, characteristic of red mangroves, is generally very dense and serves to entrap most of the organic debris produced in situ. The accumulation of organic matter by mangrove proproots, added to the debris from frequent breakage of the upper canopy structure by winds and storms, results in rela-tively large amounts of organic matter in the soils of the fringe forest.

2.2.2 ~0f N Landward of the fringe forest is a broad area characterized by sparsely-distributed individuals of very short (generally less than 2 m [7 ft] tall) red mangroves. Interspersed with these dwarf red mangroves are equally short individuals of the black mangrove (Avicennia gezvninan8), and the white mangrove (Laguncula~ia

~acemosa). This area, known as the dwarf, or scrub, mangrove zone, is found along the lower southeast coast of Florida and the Florida Keys. The dwarf mangrove zone occupies about 30/ of the study area 2-4

(see Section 4.5.3 Dwarf Mangroves). Also observed in this area are black rush and scattered clumps of salt grass. Figure 2-2 shows the frequency of the occurrence of plant species in 75 sample quadrats located in the dwarf mangrove zone.

2.2.3 Black Rush/Salt Grass Just landward of the dwarf mangrove area is a zone composed of black rush (t'uncut zoemezianus) and salt grass (DistichiEis spica'). Occasional isolated individuals of each of the mangrove species are also present. Frequency of species occurrence in the black rush/salt grass zone is given in Figure 2-3. Also character-istic of this zone is a well-developed blue-green algal mat which covers the surface of the marl substrate.

2.2.4 Saw Grass The upland vegetation zone on the study property is dominated by saw grass (Clad~urn jamaiceneis). Unlike the familiar saw grass expanses of the Everglades, this zone has a large amount of open area in which the marl substrate is exposed. A thin layer of algae is present in this area, but it is not so well defined as that in the black rush/salt grass zone (Figure 2-4), largely due to the presence of fresher water.

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DISTI CHILI S SP I CATA CRINUH AMERICANUH MIKANIA SCANDENS TALI NUM PANI CULATUH ELEUSINE INDICA PLUCHEA ROSEA SCHOENUS NIGRICANS LAGUNCULARIA RACEHOSA LIPP IA NODI FLORA PROSERPINACA PALUSTRIS VAR. PALUSTRIS SABATIA SESUVIUM PORTULACASTRUH BAT IS MARITIMA PENSTEHON

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2.2.5 Hammocks One of the striking features of the study area is the presence of hammocks. Hammocks are slight promontories covered with dense shrubs and trees. From an aerial perspective, the hammocks are "teardrop" shaped with the rounded "heads" pointing inland and tapering "tails" directed toward the shoreline. Forested hammocks with this distinctive shape and spatial pattern are found in areas where the general topography is flat and there is a characteristic unidirectional surface water flow pattern. The hammocks in the area range in size from less than 0.10 hectares (0.2 acres) to over 10 hectares (25 acres), and occur in approximate density of 40/km (15 miles ) (Snedaker, 1976). The tallest trees within the hammocks are 3 to 4 m (10 to 13 ft.) taller than the surrounding dwarf forest, which has a mean height of approximately 1.5 m (5 ft.). Any of the four mangrove species may be encountered within a hammock', red and black mangroves dominate in the more saline areas, and in the more inland areas the hammocks are increas-ingly dominated by buttonwood, particularly around the fringes. In the more inland areas, the dominance is increasingly shared by trees such as Australian pine (C'asucuina equieet~folia), Brazilian pepper (Sohinue tezebinthifoHus), and other exotic and native plants common in subtropical south Florida. The more inland hammocks eventually grade into the strand or island forests of the Florida Everglades, 2-9

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Scattered over the study area are two types of hammock which are described as either freshwater or saltwater depending upon the species composition. Saltwater hammocks are largely comprised of red mangroves, but both the black and white mangroves, and occasionally buttonwoods (Conocmpus ejecta), are present (see Figure 2-5). These hammock trees .are significantly taller than the surrounding dwarf forms. Saltwater mangrove hammocks generally occur in inland areas along depressions which channel runoff to the shoreline. They differ slightly from freshwater hammocks in that they are found in areas that are only slightly elevated relative to the surrounding area.

Found in the dwarf and black rush/salt grass zones, they are generally "teardrop" shaped. No true understory and generally few seedlings are found in the interior of the saltwater hammocks. A few herbaceous species such as glasswort (SaEicozmia uirginica), salt grass (Distichs'Lis spica'), and batis (Bat~e mcuitima) form the dominant ground cover, but 'they are usually quite dispersed and a continuous cover is seldom formed.

The brackish water hammocks, generally more rounded than the salt-water hammocks, are found in the upper black rush/salt grass and saw grass zones. These hammocks receive fresher water from rainfall runoffs, as evidenced by the species composition (Figure 2-6). Also found in brackish hammocks are the palmetto (Sabal palmetto) and the leather-fern (Acrostichum a+sewn). The brackish water hammocks are more diverse than the saltwater hammocks, and may contain some mangroves.

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0 SPECIES Figure 2-5. South Dade Area saltwater hammock vegetation inventory.

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0 SPECIES Figure 2-6. South Dade Area brackish water hammock vegetation inventory.

2-12

I Both saltwater and brackish water haranocks are characterized by large accumulations of peat which sometimes reach to the bedrock.

The peat creates a reducing environment and any standing water in the hammocks is usually highly colored, indicating high organic matter content.

A representation of the spatial distribution of these vegeta-tive zones, shown in Figure 2-1, shows that the boundaries delineating the vegetative zones are roughly parallel to the shoreline. The acreage of the vegetation zones described above is given in Table 2-1.

2-13

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TABLE 2-1 VEGETATION ZONE ACREAGE OF THE SOUTH DADE SITE Percent Ve etation t e Hectares Acres Covera e Fringe forest 142.0 (350) 3.3 Dwarf mangrove 1304.0 (3222) 30. 7 Black rush/

salt grass 424.4 (1049) 10.0 Saw grass 1630.3 (4028) 38.3 Saltwater hammock 264 ' (654) 6.2 Brackish water hammock 488.1 (1206) 11. 5 Total 4252.5 (10509) 100.0 2-14

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2.3 SOIL ANALYSES AND CHARACTERISTICS 2.3.1 Ma or Soil T es Miami oolite The geologic formation underlying the surface in the South Dade study area is Miami oolite. This bedrock is a soft, sandy limestone, containing as much as 95! calcium carbonate, and consis'ting of small spherical ovules. This rock of marine origin is believed to be Pleistocene in age (Snedaker, 1976).

Depth to bedrock varies from about 1.2 m below the surface to occasional outcroppings which broach the surface of the soil (see Section 2.3.2, Soil Stratigraphy).

Marls Overlying the Miami oolite is a nonstratified calcitic mud or marl similar to that found in other environments in south Florida. Marl is formed from carbonates transported in freshwater by heavy seasonal rainfall. These rains dissolve calcium and magnesium carbonates found in the soft limestone outcroppings common in Dade County. Carbonate-laden water slowly flows into regions of higher salinity and pH which causes precipitation of calcium and magnesium carbonate crystals.

These sink to the bottom of standing or slow-moving pools to form a blanket of white, finely divided material which looks similar to white or gray-white chalk and is called calcitic mud or marl.

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The surface of the marl is generally covered by an inch-thick blanket of periphyton, mostly blue-green algae. The accumulation of calcitic sheaths from the blue-green algal mats also contribute to the calcitic muds. The mud is cream colored when pure, but darker brown when mixed with various amounts of organic matter.

The junction between the mangrove salt marshes and the fresher water wetlands is a prime location for calcitic mud accumulation.

This region appears on aerial photographs as a bright band bordering the coast (Figure 2-7).

Peats The distribution of peat deposits at the South Dade Site varies from scattered pockets interspersed among the calcitic mud to more cohesive masses of up to 2 meters in depth. This peat appears reddish-brown when fresh, but turns darker brown to black when exposed to air, and grayish-brown when mixed with carbonates.

The peats of this region are primarily red mangrove peats that occur in marine situatiOns and in the subsurface of present-day fresh-water areas. Red mangrove peat is a fibrous, spongy, reddish-brown material composed of dead (and sometimes living) roots and other de-graded plant products. The presence of red mangrove peats spaced between layers of calcitic mud strongly suggests that the region has fluctuated between marine and freshwater influences during its geological past.

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t" +"

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ure 2-7 8 band of calcitic ad deposi-i;ion LL L

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-";paratfel Xo -shoreline, and study transec+

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station locations. I aq

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2.3.2 Soil Characteristics Soil Sam 1in Station Locations (For Stratigraphy, Bulk Density, Carbon/Carbonate and Salinity Studies)

The stations (Figure 2-7) which were examined for the soil stratigraphy, bulk density, carbon and carbonate, and salinity studies are indicated in each respective section. For purposes of discussion, Stations 1-9 are characterized as sawgrass vegeta-tion; Stations 10-17 are in the black rush/sa'It grass zone; Stations 18-26 are in the dwarf mangrove zone; and Stations 26 to Card Sound are in the fringe forest.

Soil Stratigra h Methods - Core samples were taken at 17 transect locations by means of a piston core sampling device. This device was designed to obtain relatively undisturbed and uncompressed core samples of the marl and peat layers. Core samples were extruded in the field on a portable table, split into two halves and described. Color, origin of root material, gastropods, carbonate content, water content and any allochthonous (deposited away from point of origin) material were reported at their corresponding depths. After this, the cores were sealed with a plastic wrapper and then covered with aluminum 2-18

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foil. The samples were frozen upon their return to the laboratory.

Samples of each core were cut into 5 cm intervals from one-half of the sample, then dried, ground and weighed out into sample splits for carbonate, ash-free .weight, and elemental analysis by atomic absorption. Additional core samples were taken with a 3.8 cm inside diameter PVC cylinder, which was stoppered and brought to the laboratory intact. At the laboratory the soils were extruded onto waxed paper and described 'as to color, origin of root material, gastropod shells and any unusual materials present. The cores were then cut into lengths representing the top,l5 cm of the soil, the second 15 cm of soil, and in the cases of some of the deeper cores, the bottom 15 cm of soil. These 15 cm lengths were placed in individual glass dishes and oven-dried at 70'C to a constant weight. The samples were then ground to pass through a 0.84-mm mesh screen and placed in small manila envelopes.

Results (Snedaker, 1976) - Figure 2-8 is a diagrammatic representation of the subsurface units encountered during core samp-ling. White calcareous mud (Perrine marl) was ubiquitous throughout the transect and was always present in the upper 10 cm of the core samples. This mud is typically more gray in color at the seaward stations and may be of marine origin at these particular locations.

Freshwater gastropods were common constituents of these muds and were also found within red mangrove peat.

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SAW GRASS BLACK RUSH - SALT GRASS DWARF HANGROVE FRINGE FOREST 1 2 4 5 6 7 8 9 'l1 12 17 18 19 20 21 22 23 26 27 29 3'1 32 0

10 20 Vertical scale 30(centimeters) Periphyton (surface only)

Horizontal scale (meters) 0 White Calcareous Hud Mixed Juncus 8 Rhi zophorn Peat

~Calcareous

~8 Juncus Rhizophorn Peat Rhi zophora Calcareous Juncus Peat Peat Rhi zophora Peat ggg Figure 2-8. Soil stratigraphy at l7 stations in different vegetation zones.

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Red mangrove peat was a common deposit. This peat consists of a dense mesh of intertwined roots and rootlets and fine-grained organic or calcareous interstitial material. This peat is reddish-brown in color; when mixed with carbonate it is characteristically a dark gray or gray-brown color. In some cases the peat has a mottled appearance due to irregular mixing of root material with the calcareous mud. Older red mangrove peat is quite black and contains roots with dissolved cortices. Freshwater gastropod shells were usually abundant but quite fragile or partially dissolved from the organic acids within the peat. The red mangrove peat under the scrub mangrove was slightly different from that which formed under red mangrove hammocks in that the hammock peat was distinctly more reddish and "clean" in appearance. Apparently, hammock peat Y

lacks the copious amounts of fine-grained organic matrix that is associated with scrub mangrove peat.

Calcareous peat or calcareous mud containing appr'eciable amounts of red mangrove root material was usually found under the white calcareous mud. In some cases, black rush roots occurred with red mangrove roots, but only in the upper stations of the transect.

The color varied from white to gray-brown, indicating a change in the carbonate-organic ratio within the peat matrix.

Black rush peat was found at stations northwest of Station 15.

This peat had a yellowish-brown or. grayish-brown color and displayed an 2-21

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intertwined mass of small roots and rootlets with a fine-grained matrix penetrated by larger roots and an occasional black rush leaf fragment. In general, black rush peat has a slippery feel and becomes sticky when pressed between the fingers.

Fine fragments of limestone bedrock were also present at the base of the cores. In a few cases, larger fragments were found as much as 10 cm above the contact with the limestone. Apparently, root growth has displaced these fragments from their original position at the limestone surface. The presence of these fragments indicates that a reaction between the limestone and overlying peats is causing calcium carbonate to decompose from the limestone surface.

The geological significance of the stratigraphic sequence is difficult to interpret because the peat accumulations are autoch-thonous and are not subject to the layer-cake stratigraphic principles so commonly used. The freshwater calcareous mud was probably the earliest sediment type formed on this coast. The fringe forest may also have been present at the incipient stages of carbonate deposition. At some later time, the mangroves began to colonize the calcareous mud areas. Evidence for this is tenuous at present, but the difference in gastropod shells within the peats and the mud is striking. It is possible that the growth and expansion of peat accumulating in the active rooting zone have dissolved the original matrix of carbonate silt and left behind the coarse, relatively 2-22

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insoluble gastropod shells. If peat accumulation occurred largely as a result of root addition and growth (as suggested by the lack of leaf, twig and bark in the peat mass), then replacement and displacement of the calcareous mud would occur within the active rooting zone.

Bulk Densit Methods - Samples for the determination of the bulk density of surface soils were taken at six stations along the South Dade study transect. These samples were representative of the four vegetation zones and the two hammock types. Ten 30-cms samples were taken from several cm below the surface at each site and placed in plastic soil sample bags. The samples were oven-dried at 70'C to constant weight and then weighed. The bulk density was calculated as g/cm~.

Results - The bulk density measurements for soils in the South Dade study area are important in the determination of other soil properties. Soil porosity and the estimation of the mass of a sample of soil too large to be conveniently weighed are both dependent on the bulk density. Bulk density determinations for the various stations and soil areas are given in Table 2-2.

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TABLE 2-2 BULK DENSITY MEASUREMENTS FOR SOUTH DADE AREA SOILS Station Habitat Saw grass 0.474 Black rush/salt grass 0.477 Hammock 0.265 16 Black rush/salt grass 0.531 23 Dwarf mangrove 0.578 23 Hammock 0.378 30 Dwarf mangrove 0.501 30 Hammock 0.397 37 Fringe forest 0.143 2-24

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The hammock samples are less dense than all other samples with the exception of fringe forest samples.

Carbon and Carbonate Anal ses Methods - Both organic and inorganic carbon were determined for the South Dade study area soils. Several samples were analyzed for total carbon using the wet combustion method. Concurrently, samples of the same soil were analyzed for carbonate carbon by the volumetric calcimeter method. The difference between these two amounts was taken to be the organic carbon content. The soil was then analyzed for organic carbon by the Walkley-Black wet oxidation method. All results were presented as percentage dry weight of soil (Fell, 1976).

Results - The results of the carbon analyses demonstrated that the total carbon content of the soils was quite varied, with a high value of 35.01% in the peat soil at Station 2 and a low value of 10.13/ in the lower depths of the marl soils at Station 8. The total carbon content has been divided into its organic and inorganic components. Inorganic carbon comprised from 0.09K to as much as 10.6/ of the soil carbon, while organic carbon ranged from 1.12/

to 34.33K of the total soil carbon. The percentage of organic carbon was about twice as much in the surface peats in the hammock at Station 2 as that in the surface peats in the hammock at Station 30.

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This could possibly reflect the differences in the amount of tidal scouring present between the two stations. Calcium carbonate formed a major portion of the soil, comprising up to 90 .805 of the soil. The surface sediments consisted mainly of calcium carbonate.

The analysis of the calcium, magnesium and strontium contents of the calcium carbonate fraction provided valuable informati on on the character and composition of the precipitate. Table 2-3 is a summary of the averages of the composition of the marls and peats at three depths over the entire transect. The concentrations of all three elements were influenced by the amount of organic matter present. Calcium decreased with increasing organic matter, while magnesium and strontium both increased with increasing organic matter. Calcium content increased slightly with increasing proximity to Card Sound and with depth. Magnesium also showed a slight increase both down the transect and with depth through the soil column.

Soil Salinit This study was conducted to determine the amount of dissolved chlorides (salts) in the interstitial and surface waters from soils of the South Oade study area.

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TABLE 2-3 AVERAGE CALCIUM, MAGNESIUM AND STRONTIUM COMPOSITION OF THE CARBONATE FRACTION OF THE MARLS AND PEATS ALONG THE SOUTH DADE STUDY TRANSECT a sons an Habitat Depths  % Calcium  % Ma nesium  % Strontium MARLS Saw grass Stations 1-9 0- 6 97.08 2.74 0.048 6- 12" 97.58 2.28 0.060 12- 18" 94.30 5.50 0.070 Black rush/ Stations 15-17 Salt grass 0- 6 96.90 2.90 0.060 6- 12" 96.50 3.30 0.045 12- 18" 96.66 3.17 0.066 Dwarf mangrove Stations 21-26 0- 6" 96.83 2. 97 0.070 6- 12" 95.70 4.12 0.068 12- 18" 97.40 2.45 0.060 Fringe forest Stations 29-32 0- 6" 96.07 3.57 0. 073 6- 12" 94.90 4 '5 0.089 PEATS Brackish water hammock Stations 1-17 0- 6" 70.45 29.35 0.100 6- 12" 80.13 19.63 0.112 12- 18" 85.00 14.70 0.060 Saltwater hammock Stations 18-32 0- 6'-

94.75 5.15 0.070 12" 92.10 7,80 0.080 12- 18" 88.85 11. 00 0.045 2-27

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Methods - Data for surface water and ground water salinities were obtained from Automatic Hydrolab recorders, described in Section 4.4.2, Hydraulic Studies. Chlorinity values for Stations 2, 9, 16, 21, 30 and 37 (Table 2-4) were used to construct graphs of salinity changes along the transect for 1974. In May and October 1976, additional salinity surveys were made along the transect using an American Optical refractometer.

Results - Figure 2-9 shows the variations recorded in surface and ground water chlorinities on the South Dade study area for 1974. The maximum chlorinities occurred at Station 30 during the spring when reduced rainfall and increased insolation concentrated the salts in the tidal 'waters. Decreased chlori n-ities at this time at the upper transect stations may reflect ground water input, which would dilute the seawater. The chlor-inity measurements at Station 37 show little variation in the I

Card Sound waters throughout the year. The average chlorinity at this station is approximately 19 parts per thousand (%,)

which is essentially that of "normal" seawater. 'Chlorinity values may be multiplied by 1.86 to approximate salt concentration in parts per thousand. During the latter part of the year, when standing water covered Station 2, the chlorinity at the upper transect stations was about 5%,, which is about 27/ of normal seawater.

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TABLE 2-4 SALINITY IN PARTS PER THOUSAND (%o )

FROM GROUND WATER OF MAJOR VEGETATION AREAS Station Number Area %o 37 Fringe forest shoreline 34 30 Dwarf mangrove/f ringe f orest 38 21 Black rush/salt grass 28 16 Black rush/salt grass 18 Saw grass 16 Saw grass 2-29

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BLACK RUSH/

SAW GRASS SALT GRASS DWARF MANGROVE FRINGE FOREST CARD SOUND 45 25 40 30 20 10 5 0

0 0 0

0 0 (a) MEAtt SURFACE WATER 0 0 I

z 40 z 22.5 20 Vl 30 15 20 10 10 (b) MEAN GROUND WATER 0 37 9 16 21 30 DISTAttCE ALOttG TRANSECT (m X 100)

Figure 2-9. Salinity and chlorinity values along study transect.

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Salinity values at Station 9 varied more than at any other station. Because data from Station 16 were limited they did not reflect the true variation observed at the station. However, the figures do indicate a close correlation between surface and ground water sal ini ties.

The highest salt concentrations were observed in the soils from the dwarf mangrove zone. This hypersaline region landward of the fringe forest comprises 30.66! of the South Oade Site.

Tidal cycles vary in amplitude and thus the distance traveled inland also varies; the soils are subject to repeated periods of saturation and drying by evaporation which effectively concentrates the soluble components of seawater and brackish ground water.

Also, drainage of the region is generally slow. Thus, evaporative processes build up the concentrations of salts and minerals to levels which are toxic to all but salt-tolerant species such as mangroves ~ Soil salinities from the open flats have been measured as high as 80.3'/, in isolated instances, which is roughly two and one-half that of bay waters.

Salt-tolerant plants proliferate in regions of high salt concentrations not due to metabolic need for excessive chloride, but due to their ability to survive where other plant species, 2-31

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competing for the same space, light, and nutrients, are unable to withstand the osmotic stresses placed upon them by the environ-ment.

Soil Sam lin Locations (for ATP, Soil Moisture, pH, and Organic/Inorganic Carbon Studies)

Transect stations selected as representative of the differ-ent ecotones were 2, 6, 10, 14, 18, 20 and 30. Soil samples consisted of cylindrical cores about 5 cm in diameter and 25-50 cm in length. Multiple sections of approximately 1 cm were taken down the length of the core for analysis. Subsurface sampling was done because undegraded plant detritus was present at varying depths in test cores. Also, water levels fluctuated, which could affect cyclic exchange mechanisms in the transport of nutrients and degraded products of metabolism.

These samples were analyzed for ATP, soil moisture, pH, and organic and inorganic carbon.

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ATP - Studies were undertaken to defi ne biological activi ty in South Dade soils. Biological activity was determined by measuring the adenosine triphosphate (ATP) content of the soil.

ATP is part of a system of chemicals found only in living cells; thus measurement of ATP concentrations provides an indirect measure of living organisms whether they are bacterial, protozoal, or higher life forms. High ATP concentrations indicate biologi-cal activity, but do not differentiate between plant or animal tissue. The relatively constant ratio of ATP to carbon in living cells permits estimates to be made of living biomass which cannot be otherwise calculated from the samples while i n the field.

Determination of the ATP content of soil collected from Stations 2, 18, and 30 in open land areas well away from the hammock area corresponded to other samples taken for carbon analysis, pH, and moisture. Open land collection sites were considered representative of the predominant character of the transect. Additional samples were taken from the "drainage tail" of hammocks at Stations 2, 18, and 30 for comparative purposes to confirm an anticipated higher biomass in soil from areas of higher plant detritus production.

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Results of ATP concentration analyses at 5-cm soil depth intervals at Stations 2, 18, and 30 are" shown in Table 2-5 . Con-sidering only the mean concentration of ATP at all depths of soil, it appeared that the concentration progressively decreased from Station 2 to Station 30. The relatively constant rate of decrease of ATP concentration as a function of soil depth was about the same at Stations 2, 18, and 30. The ATP concentration at any level was about 50% that of the preceding level (Fi ncher, 1976).

Similar determinations of ATP concentrations were made on soil cores from the "drainage tail" of hammocks in the areas of Stations 2, 18, and 30. Expectations were for higher levels of ATP on the premise that these areas received higher quantities of plant detritus which would support a larger biomass, measured as ATP, than in the non-hammock or "open" areas of the transect. Such expectations were found to be true at all stations in the top 1 cm of soil, as shown in Table 2-6 . At Station 2, ATP concentrations at 5-15 cm of depth were equivalent in the "drainage tail" and "open" area sites. However, the two-fold higher concentration in the surface layer of the "drainage tail" at Station 2 declined more rapidly with soil depths The concentration of ATP in the "drainage tail" decreased 64% with each soil stratum,,whereas in the "open,"

non-hammock location, ATP decreased 50% with each soil depth. The rate of decrease with soil depth was also higher in soil from the "drainage tail" at Stations 18 and 30.

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TABLE 2-5 ADENOSINE TRIPHOSPHATE (ATP) IN SOIL SAMPLES FROM NON-HAMMOCK AREAS NEAR STATIONS 2, 18, and'30 Mean concentration of ATP - g / dr soil Soil Depth CN Station 2 Station 18 Station 30

2. 38 1. 01 0. 66 1.20 0.57 0.37 10 0.60 0.32 0.21

0. 29 0.18 0. 12 20 0.14 0.10 0.06 25 0.07 0.05 0.04 30 0.04 0.03 0. 02 Rate of decrease per depth interval, 1 50 43 2-35

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TABLE 2-6 ADENOSINE TRIPHOSPHATE (ATP) IN SOIL SAMPLES FROM 'DRAINAGE TAIL'F HAMMOCKS NEAR STATIONS 2, 18, and 30 Mean concentration of ATP - u / dr soil Soil Depth (cm Station 2 Station 18 Station 30 4.78 4.47 1.66 1.90 0.66 10 0. 60 0. 76 0.26 15 0. 21 0. 30 0.10 20 0.-1 2 0.04 25 0.04 0.01

'0 0.02 0.006 Rate of decrease per depth interval,'4 64 57 60 2-36

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Concentrations of ATP at the same soil depths in the "drainage tail" were equivalent at Stations 2 and 18. Both locations had higher ATP concentrations than Station 30 .

In summary, biomass in the soil, measured as ATP, appeared to decrease in concentration in the sequence of Stations 2, 18 and 30, particularly in the surface layer of soil in the "open" or non-hammock areas. Highest biomasses were recorded at Station 2.

Differences in biomass at the three stations were less evident as a function of soil depth. At depths of 25-30 cm, the biomasses were equivalent and about 2-3X of the concentrations at the soi 1 surface.

Although initially higher at the soil surface in the "drain-age tail" of the hammocks, the rate of decrease of biomass with soil depth was more rapid and was equivalent to the biomass found in lower soil strata in the "open" or non-hammock areas.

I Generally, these findings suggested a gradient of a biological system which decreased from a comparatively high level in the "upland" area to a lower level in the direction of Card Sound. Also, black rush/salt grass soils appear to be less biologically active than saw grass soils.

Soil Moisture Soil water content was found to be about 57.,0/ by weight in samples collected during the months of Hay 1974-5 and October 1974.

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These determinations were made on standing core samples in the lab-oratory and therefore the results are a measure of the water-retaining capacity of the soil. The small variation in the water content measurements shows a relatively constant high water content at Stations 2, 6, 10, 14, 18, 20, and 30. Higher water content (about 82%) was found in cores with a high peat content.

~So i1 H Values of pH, organic carbon, and inorganic carbon in soil at Station 2, 6, 14, 18, and 30 were functionally related to depth pro-files of soil. Average values are shown in Figure 2-10. The pH of 7.66 at Station 2 was lower than the values at Stations 18 and 30 at all depths. At these latter two stations a transitional zone was found at the depth of 9-14 cm; the upper soil levels had a pH of 8.04-8.05 and the lower levels a pH of 7.86-7.89; again indicative of "dropping out" of ions in upper soils.

Or anic and Inor anic Carbon Organic carbon is distinguishable from inorganic carbon in that organic carbon is produced by plants and animals, including bacteria, and inorganic carbon sources are carbon dioxide (C02) and carbonates, such as those found in limestones and marl soils. Organic carbon determinations therefore provide useful evidence of biological 2-38

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STA 2 STA 6 STA 14 STA 18 STA 30 a b O C)

CJ C)

CO I CO 10 E E

O 20 O

LIJ 30 CO (D

40 50 a = pH b = Organic carbon (% by weight) c = Inorganic carbon (% by weight) 2.54 cm = 1 in Figure 2-10. Depth profiles by stations and parameters, 2-39

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Organic carbon concentrations were stratified in the soil profiles. The 4.6X concentration of organic carbon in the top 10 cm of soil at Station 2 was similar to values obtained below 10-15 cm at Stations 14, 18, and 30. Above 10 cm the organic carbon concen-tration of 1.9-2.4/ was similar to the uniformly constant value of 2.4X at Station 6. Stations 6, 14, 18 and 30 had organic carbon concentrations that were about 50% lower than the upper 10 cm of Station 2. The highest concentration of organic carbon recorded was 14/. This value was found below 10 cm at Station 2 in the saw grass zone of the transect.

Inorganic carbon (principally carbonates) concentrations were uniformly high (44.9-47.4'4) in the top 10 cm of soil at Station 2, and at 30-35 cm at Stations 6, 14, and 18. Station 30 had a low concentration (42.2/) up to 10 cm in depth, and a lower concentration (28.2%%d) to about 50 cm in depth. This lower concentration was close I

to the 25.3Ã value found below 13 cm at Station 2.

Organic carbon stratification is shown in Table 2-7. The amount of organic carbon in the top 0-10 cm at Stations 2, 18, and 30 was less than that below 11 cm. An inverse relationship of inorganic carbon and soi 1 depth appeared to be the trend, except at Station 18 where stratification was not noted.

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TABLE 2-7 DEPTH ANALYSIS OF ORGANIC AND INORGANIC CARBON CONTENT OF SOIL Carbon Content of Soil m / Dr Soil Station No.

Sil Interval ph cm

~0i N .

C b Mean N Mean Ratio of Carbon Or Means anic:Inor anic 0-10 6 46.0 6 459.2 1:10 12 24 7 140.1 7 253.3 1.2 0- 8 19.6 1:24 18 16 474.0 11-30 50.8 1:9 0-10 24.0 442.0 1:18 30 12- 24 36.0 327.0 1:9 26- 48 51.5 260.4 1 5

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Stratification of carbon with soil depth suggests inflooding of silt-bearing water, probably marine in origin, which, when it recedes, leaves a deposit covering existing vegetation. The result-ing organic deposits and subsequent plant growth provide nutrient substrates for carbon-utilizing bacteria. Subsequent bacteriologi-cal findings (in Section 2.3.3) indicated that a significant portion of the carbon-utilizing bacteria are found at the surface and in the lower 10-48 cm strata of soil.

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2.3.3 Soil Ni cr obiol o The objective of this study was to provide information on the bacteriological content of the soils in the South Dade Area as one index of the energy turnover rates, and thus the productivity of the area. Selective methods of analyses were used which would recover and characterize the broadest number of species of bacteria which utilize organic compounds as sources of energy and growth. Such bacteria are instrumental in the cycling of carbon compounds in the soll .

methods Three sites along the study transect were chosen as typical of the broadly discernible zones characterized by saw grass, black rush/salt grass, and dwarf mangroves: Stations 2, 18, and 30, respectively. Station 30 was marine, Station 18 was influenced by both brackish and freshwater sources, and Station 2 was predominantly freshwater in character.

Selection of representative sites was necessary to recover as many bacterial types as possible from different soil habitats.

Since no single culture medium supports the growth of all soil bacteria, knowledge of probable essential salt growth requirements by marine forms provided more representative culture yields.

Soil samples consisted of cylindrical cores about 5 cm in diameter and 25-50 cm in length. Enumeration of viable bacteria at various soil depths was done under conditions that isolated 2-43

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aerobic (those requiring oxygen), facultative anaerobic (capable of living in the presence or absence of atmospheric oxygen), and obligate anaerobic heterotrophic (growing only in the absence of oxygen and using carbon as an energy source) bacteria.

Results Numbers of bacteria in soil - Determinations of the aerobic and facultative anaerobic bacteria content were made from Stations 2, 18, and 30. Both groups use organic compounds for energy and growth.

Numbers of bacteria are presented as colony-forming units (CFU),

which is a standard technique for expressing bacterial populations.

Table 2-8 gives CFU counts of the three typical habitats at various soil depths.

In all cases, larger populations of bacteria were found on the surface, and numbers decreased as a function of soil depth.

Also, the rate of population decrease was about the same for all three stations. Bacterial numbers appeared to have an inverse relationship to the soil content of organic carbon, which was found to increase with soil depth.

The highest frequency of bacterial spores and/or thermo-duric bacteria (those that form heat-resistant spores) was found in the 0-15 cm depth interval. Below this depth it was observed that these bacterial forms occurred at a frequency of 10% or less.

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TABLE 2-8 DERIVED COUNTS OF COLONY-FORMING UNITS (CFU)

OF AEROBIC AND FACULTATIVE ANAEROBIC BACTERIA Soil Depth Stati on cm 18 30 2317 1824 854 1567 1404 551 10 1059 1081 356 716 832 229'48 20 484 641 25 493 95 30 380 61 35 292 39 40 25 Rate of decrease per depth interval, X 32 23 35 CFU=Nx10 /g dry soil, single core values.

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This suggests that populations below 0-15 cm are more sensitive to heat. This population, although smaller than that at upper soi 1 depths, was more versatile in the use of different carbon compounds for metabolism.

Taxono of Soil Bacteria - About 870 bacteria were isolated and studied in pure culture. Each culture was examined for a possi-ble 252 characteristics including physiological, metabolic and mor-phological categories. Data were computer processed and coeffi-cients of association were calculated. This is a numerical expression which relates the degree of overall similarity of one bacterium to another. Summation of analysis of clusters of bacteria having co-efficients of association equal to or greater than 80K is shown in Table 2-9.

Cluster analysis of bacteria isolated from Station 18 showed high percentages of inclusion (sameness) in clusters at al'1 soil depth intervals. Homogeneity of bacterial types throughout the soil column was also greater at Station 18. There was a general absence of relatedness of isolates from Stations 2 and 30.

Ph siolo ical and Metabolic Characteristics All bacterial populations from Stations 2, 18, and 30 were dominated by forms able to live under conditions of reduced oxygen. Populations of all three stations were dominated by true facultative anaerobes at depths below 2-46

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TABLE 2-9 CLUSTER ANALYSIS OF SOIL ISOLATES SHOWING GROUPS WITH

> 80/ COEFFICIENTS OF ASSOCIATION Station 2 Stati on 18 Station 30 Soil No. of No. of No. of No. of No. of No. of De th cm ~Grou s ~OTU/Grou u ~Grou s ~OTU/Grou o ~Grou s ~OTU/Grou u 5;3 5;3 2'2 7'2 6s3 10 5;4 12 4;2 14 8;7 16 5;2 4;3;3;2 18 3'2 5;4;2;2 21 6;3 22 6;2 26 7'2'2 30 4;4 34 8;2;2;2 2'2'2 38 6;3;2;2;2 5;4 OTU Operational Taxonomic Unit is used instead of generic and specific names for purposes of computer grouping by characteristics. One OTU is equal to one isolate.

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12-14 cm. The near-absence of soil bacteria growing only in the presence of atmospheric oxygen reflects the low oxygen tension usually found in water-saturated soil.

The optimum temperature for growth for the majority of isolates was 25'C, in a range of 15-35'C. Isolates from Station 18 showed a wider temperature range (15-45'C) of growth than was found at Stations 2 and 30.

More acid-tolerant (pH 5 .0) forms occurred at depths below 6-10 cm. Station 2 showed a generally less sensitive population capable of growing in pH ranges between 6.0 to 8.0. These findings suggested that different bacterial populations existed at the three stations as well as at different intervals of soil depth.

Separation of the bacterial populations of the saw grass, black rush/salt grass and dwarf mangrove zones was indicated by the ability of .the bacteria to grow in a salt-free medium or by a de-pendence on the salts of sodium, potassium, calcium, or magnesium.

Of the bacteria from the saw grass soils, 80K were not dependent upon salts for growth. In growth media where three of the four elements (sodium, calcium, magnesium, potassium) were present, only bacteria from Station 30 showed a significant dependence on sodium coupled with some dependence on either calcium or magnesium. Isolates from the black rush/salt grass zone demonstrated no dependence on a single element.

Growth occurred on any three elements in combination.

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Carbon metabolism - Isolates from the three zones were examined for their ability to hydrolyze (break down) a spectrum of compounds known to contain complex carbon structures. A summary of these results expressed as averages throughout the soil column is shown in Table 2-10. Generally, isolates capable of splitting the compounds were distributed throughout the soil column. Bacteria capable of splitting chitin are of interest, as this substance is found in the skeletal material of invertebrate animals such as crabs and insects. The ability to degrade cellulose, found in plant tissue cell walls, was not widespread but was encountered in the saw grass soils.

Nitro en metabolism - Isolates from the saw grass soils showed the highest frequency of using most available compounds as nitrogeneous sources. About 14 isolates were able to use atmospheric nitrogen.

Bacterial populations in the dwarf mangrove zones were less able to use nitrogen-containing compounds. Atmospheric nitrogen was used by 18/ of those isolates.

Isolates from black rush/salt grass zones were essentially unable to use nitrogen from available sources.

Reduction of nitrate to nitrite was done by isolates from all soil depths at Stations 2 and 30. Many bacteria were able to use the 2-49

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TABLE 2-10

SUMMARY

OF HYDROLYSIS OF VARIOUS SUBSTRATES BY ALL ISOLATES IN A SOIL COLUMN STATIONS 2, 18, 30 Avera e fre uenc of h drol sis Station 2 Station 18 Station 30 Total OTU Total OTU Total OTU Substrate Tested l Tested X Tested l

Aesculin 31 198 33 252 52 270 Araban 32 136 13 248 16 165 Casein 53 192 72 242 79 244 Cellulose 21 198 0 270 Chitin 17 '95 3 194 28 201 Gelatin 16 197 33 252 270 Starch 59 193 62 244 74 244 Tri butyrin 69 179 61 215 60 238 Xyl an 193 171 213 Depth of Soil Column (cm): 21 38 38 2-50

I oxygen found on nitrate when grown under conditions of reduced atmospheric oxygen tension. These conditions would occur when soils were waterlogged. The reduction of nitrates by such bac-teria in the soil is probably an adaptive mechanism for survival via nutrient cycling in environments with reduced oxygen.

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2. 3.4 Soil Profile Introduction The objective of the soil profile study was to make an eval-uation of the surface and subsurface topography of a mangrove hammock.

The hammock selected for this study was located in an area of uncon-solidated, high-magnesium calcite, interspersed with small red man-grove peat units, over the limestone bedrock (l1iami oolite) at a depth of 1 to 2 m. The study hammock was wetted by at least all high-high tides, although the interior was dry for several months during the spring period of low rainfall and low-hi gh tides.

This hammock was chosen for intensive study for three reasons:

1) it had the characteristic "tear drop" shape and a core of taller trees; 2) it was representative of the 985 larger and smaller hammocks on the site; and 3) it graded into a smaller hammock which provided a second type of ecotone in addition to the dwarf forest.

The species compositon of the study hammock was exclusively man-grove, although there was evidence that other woody species, such as the palm (paurotis wrightii), were once a component of the canopy.

The evidence for the palm, in particular, was the presence of many "stumpholes" left by long-decayed palms. Other evidence for sub-tropical hardwoods included standing-dead non-mangrove trees and trunks trapped within the mangrove proproot structure.

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Methods Hammock soil transects - The study hammock (Figure 2-11) is situated some 250 meters south of Station 30, which was used as the elevation control point. To control the field measurements and ensure comparable data relative to elevation, four survey lines were shot through the hammock and elevations were taken at 1 m intervals; these lines became the study transects (Figure 2-12).

The main transect (A) was shot parallel to the long axis of the hammock. Transect A was 240 m long and extended into the dwarf mangrove zone at both ends. Three additional transects were shot perpendicular to transect A: transect B (160 m) through the head of the hammock, transect C (140 m) through the central core, and transect D (105 m) through the tail and a'contiguous smaller hammock.

Narrow survey lines were cut to permit access of personnel and to obtain 50-m transect shots through the hammock. Stakes were set at 5-m intervals along each transect between the access paths and the undisturbed study area on the other side. All ecological measurements were made in the undisturbed portion of the transect and recorded by transect distance and elevation. The elevations were expressed as centimeters above or below transect station marker b'30+00 which was shown to be at the same elevation as points 0 and 240 of transect A.

Subsurface strati ra h At 1 m intervals along each transect, a steel rod was inserted slowly into the sediment down to 2-53

~"

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.figure 2-11 Location o$ study hammock )

in barf mangrove zone. 3 C

-c Ci Q +Oo e'.0'~ Capp C895 ga<e 1

P 4i. 1' We. ,w"4L.

'\'

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4

.! 4-0 4 P~

'0, a.

i; 0

4.

-Study-mWammcck

'" Litt1e Card. 50,un i; ii

.'\

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GROUND SURFACE ELEVATION HANGROVE HAJAHOCK PEAT 60 CALCAREOUS 18JDS WITH

-80 ROOT INTRUSION

-120 PEAT AND FRAGMENTED

-160 BEDROCK

-200 TRANSECT B . ~'NO->>r 160 SOLID 0 -260 BEDROCK TRANSECT B

-280 8 10 20 30 AIO 50 60 70 80 90 100 110 120 130 140 150 160 GROUND SURFACE ELEVATION SI0 HANGROVE HAJBNCK PEAT RAD CALCARENIS NDDS NITK 140 80 ROOT INTRUSION LI C)

-120 CN:

CD 160 PEAT AND FRAGMENTEO BEDROCK CJ -200 SOLID BEDROCK 260 TRANSECT C CS: -280 0 10 20 30 40 50 60 70 80 90 100 110 120 130 1IIO D

-~rgW~r I-CD. GROUND SURFACE ELEVATION C/D A3:

60 MANGROVE HAJAKIIJXK PEAT

-80 CALCAREOUS l%JDS WITM TRAMSECT D ROOT INTRUSION 0 105

-120 PEAT ANO FRAGMENTEO 160 BEDROCK

-200 SOLID TRANSECT D BEDROCK

-2TDO 0 10 20 30 40 50 60 70 80 90 100 105 ODeters TRANSECT A 290 GROUND SURFACE ELEVATION 0

MANGROVE HAMMOCK PEAT 60 x 8 CALCARENIS NIDS NITII

-80 ROOT INTRUSION g~

I- < 120 PEAT AND FRAGHDITEO

$o BEDROCK TRANSECT A SOLID BEDROCK 200 0 10 20 30 TIO 50 60 70 80 90 100 110 120 130 3IIO 150 160 170 180 190 200 210 220 -

230 260 ODeters Figure 2-12. Hammock study transects.

RE the surface of a secondary unit composed of bedrock fragments and peat; the depth was recorded. The rod was then forced through this unit to determine the depth to bedrock. At 10 m intervals along the transect, cores were taken with 1.75-in. diameter PVC tubes.

These cores were extruded and described in the field; a total of 52 descriPtions were made. An additional set of 16 cores, taken at 25 m intervals, was retained for detailed description and analyses.

Results Each mangrove hammock surveyed was. found to be topographically higher by a few centimeters than the surrounding dwarf mangrove community. The hammock surface was normally exposed during low tide and submerged at high tide. The entire surface of the hammock was composed of red mangrove peat, and, when surveyed in detail, showed humps and depressions which were expressions of differential rates of peat accumulation at the base of the proproots (Snedaker, 1976).

The subsurface was found to be highly irregular and variable due to the topography on the surface of the Miami oolite. The subsur-face profiles (Figure 2-12) indicated that the bedrock surface was pitted and studded with pockets and pinnacles. This type of surface is commonly found in other areas where the Miami oolite ridqe outcrops (Crai ghead, 1971) .

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A secondary unit overlay the oolite bedrock. It was composed of bedrock fragments and peat containing partially decomposed organic material with red mangrove rootlets. This unit also had an irregular surface which roughly paralleled the bedrock surface. In some instances, the unit filled bedrock depressions.

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2.4

SUMMARY

Natural plant associations were strongly influenced by two major determinants: tolerance to water of varying chloride (salt) concentrations and the distribution of high organic-containing soils, mostly mangrove peats. Zones of vegetation were delineated and main-

-tained based upon a plant species being able to withstand physiolog-ical stresses imposed by salt-induced osmotic pressure. Density and acreage of plant species were identified and described using principal vegetative characteristics as follows:

~Ff fringe pf f1

~g-d d 1 a ~ g g a dense bordering the coast

b. p1 1 f <<d red, black, or white mangroves which are not believed df to be a dwarf race or variety, but rather have dwarf characteristics imposed by high chloride concentrations and low phosphorus content of the soils.

c ~ Black rush salt rass - two grass-like species which occur between the higher saline soils of the dwarf mangroves and the fresher water saw grass habitat.

d. ~Saw rass - generally in fresher water and about one mile inland from Card Sound waters.

e. Salt water hammocks - slightly elevated oval or round masses of high organic peats which support dense stands of mangroves Brackish water hammocks - with configurations similar to salt water hammocks except that a different plant species composition occurs.

The South Dade Site soils are nonstratified calcitic muds which are composed of finely-divided calcium and magnesium carbonates. Soil depth to bedrock varies from 1.2 meters to occasional out-croppings 2-58

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which broach the surface of the soil. Scattered randomly within the calcitic mud are pockets or lenses of organic peats. These are com-prised of mostly dead roots and other degraded plant products. Peats I

may or may not broach the surface. Peat deposits which do broach the surface may support dense mangrove-dominated vegetation to form salt-water or brackishwater hammocks. Red mangrove peats spaced between layers of calcitic mud strongly suggest the region has fluctuated between marine and freshwater influences during its geological past.,

The freshwater calcareous mud was probably the earliest sediment type formed on this coast. At some later time, mangroves began to colon-ize the calcareous mud areas.

Stratification of carbon with soil depth suggests flooding by silt-bearing water, probably marine in origin, which, when it recedes, leaves a deposit covering existing vegetation. The resulting organic deposits and subsequent plant growth provide nutrient substrates for carbon-utilizing bacteria. Bacteriological findings (in Section 2.3.3) indicated that a significant portion of the carbon-utilizing bacteria are found at the surface and in the lower 10-48 cm strata of soi l.

Biomass in the soil, measured as ATP, appeared to decrease in concentration in the sequence of Stations 2, 18 and 30, particularly in the surface layer of soil in the "open" or non-hammock areas.

Differences in biomass at the three stations were less evident as a function of soil depth. At depths of 25-30 cm, the biomasses were equivalent and about 2-3X of the concentrations at the soil surface.

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Although initially higher at the soil surface in the "drain-age tail" of the hammocks, the rate of decrease of biomass with soil depth was more rapid and was equivalent to the biomass found in lower soil strata in the "open" or non-hammock areas.

These .findings suggested a gradient of microbiological activ-ity which decreased from a comparatively high level in the "upland" area to a lower level in the direction of Card Sound. Also, black rush/salt grass soils appear to be biologically less active than saw grass soils. The near-absence of soil bacteria growing only in the presence of atmospheric oxygen reflects the low oxygen tension usually found in water-saturated soil.

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3.0 KINDS AND ABUNDANCE OF NATIVE ANIMALS

3.1 INTRODUCTION

Studies were conducted to determine the kinds and abundance of native animals that use the different plant communi ties of the South Dade Site for food, shelter, and breeding. Field obser-vations and trapping techniques were used to prepare lists of the species noted.

Particular attention has been paid to any rare or endangered birds, mammals, amphibians, reptiles, fishes and selected inverte-brates. Endangered and threatened wildlife species are listed by the Fish and 'Wildlife Service of the U. S. Department of the Interior

'Federal Register 42(135):36420-36431, July 14, 1977) and by the State of Florida Game and Fresh Water Fish Commission (Wildlife Code of the State of Florida, Chapter 16 E-3, Tallahassee," Florida, July 1977). In addition to these sources, the Florida Committee on Rare and Endangered Plants and Animals (FCREPA) has prepared an Inventory oZ Raze and Endangered Biota oi Florida(1976) ~ The status categories used by FCREPA and referred to in this section are defined in Table 3-j-. All three of these lists have been used to determine which species are considered rare and endangered in Florida.

Species whose known range or habitat preference probably would preclude their occurrence on the Florida Power & Light Company 3-1

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property and in fact have not been recorded in the vicinity are not treated in this report.

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TABLE 3-1 STATUS CATEGORY DEFINITIONS EXTRACTED FROM THE-INVENTORY OF RARE AND ENDANGERED BIOTA OF FLORIDA (FCREPA, 1976)

Status Category Definition En dan ge red Species in danger of extinction if the deleterious factors affecting their populations continue to operate. These are forms whose numbers have already declined to such a critically low level or whose habitats have been so seriously reduced or degraded that without active assist-ance their survival in Florida is questionable.

Threatened Species that are likely to become endangered in the State within the foreseeable future if current trends continue. This category includes

1) species in which most or all populations are decreasing because of overexploitation, habitat loss, or other factors; 2) species whose pop-ulations have already been heavily depleted by deleterious conditions and which, while not actually endangered, are nevertheless in a critical state; and 3) species which may still be relatively abundant but are being subjected to serious adverse pressures throughout their range.

Rare Species which, although not presently endangered or threatened as defined above, are potentially at risk because they are found only within a restricted geographic area or habitat in the State or are sparsely dis-tributed over a more extensive range.

Species of Special Species that do not clearly fit into one of the foregoing categories Concern yet warrant special attention. Included in this category are 1) species that, although they are perhaps presently relatively abundant and wide-spread in the State, are especially vulnerable to certain types of exploitation or environmental changes and have experienced long-term population declines and 2) species whose status in Florida has a potential impact on endangered or threatened populations of the same or other species outside the State.

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TABLE 3-l (continued)

STATUS CATEGORY DEFINITIONS EXTRACTED FROM THE INVENTORY OF RARE AND ENDANGERED BIOTA OF FLORIDA (FCREPA, l976)

Status Category Definition Status Undetermined Species that are suspected of falling in one of the above categories but for which available data are insufficient to provide an adequate basis for their assignment to a specific category.

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3.2 BIRDS Bird populations shift locally and seasonally so that at the South Dade Site, as in southern Florida in general, there is a continuous change in the spectrum of bird species present. There-fore, any inventory of birds must take into account summer residents, winter residents, permanent residents, migratory visitors, accidental visitors, and flyovers. To further complicate analyses, birds use different parts of their range for breeding, nesting, feeding, and basking.

Bird censuses were made every two months for one year at 12 terrestrial sites and along the shoreline, of the South Dade study area. Birds were identified by sight as well as by calls and songs.

Birds frequenting Arsenicker Keys, some 9 km NE of Card Point, were also noted.

The results of the bird study are presented in Tables 3-2 and 3-3 which list the species noted, their status (e.g.,summer resident, flyovers) and the habitats in which they are usually found.

Table 3-3 lists the rare or endangered birds that have been seen on or are presumed to use the South Dade study site.

A total of 79 species of birds were observed in the South Dade study area. An additional nine bird species listed by FCREPA have been reported in the vicinity but were not noted during this 3-5

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TABLE 3-2 BIRDS FOUND WITHIN OR NEAR THE SOUTH DADE SITE (NOT ON RARE OR ENDANGERED LIST)

Habitat in which bird noted Observed Offshore Residency in air Black rush/ Dwarf Fringe (within Cocmon name Scientific name* status space only Saw grass salt grass mangrove forest Other Anhinga anhinga anhinga Permanent resident canals American Bittern Botaurus lenciginosvs Minter resident Red-winged Blackbird agelaius phoeniceus Permanent resident Bobolink Dolichonyx oryzivorus Migratory visitor Cardinal Cardinaiis cardinalis Permanent resident Chuck-will's liidow Caprimvlgus vociferus Sucmer resident Double-crested Cormorant l halacrocorax auritus Permanent resident Hourning Dove Zenai da macroura Permanent resident Mood Duck Aix sponsa Permanent resident Cattle Egret Bubvlcvs ibis Permanent resident canals Comnon Flicker Colaptes avratus Permanent resident gb v'b American Goldfinch - Carduelis tristis Minter resident gb Glue,-gray Gnatcatcher Poliopcila caerulea Winter resident gb gb gb Goat-tailed Grackle guiscal uis ma jor Permanent resident gb Cocmon Grackle gviscalvs quiscvla Permanent resident Pied-billed Grebe Podilymbus podiceps Permanent resident Herring Gull Lares argentatus Winter resident Found dead, only fragments.

'n Bayhead.

c Probably seldom lands on South Dade site.

Homenclature according to Bull and Farrand, 1977.

I' TABLE 3-2 (continued)

BIRDS FOUND WITHIN OR NEAR THE SOUTH DADE SITE (NOT ON RARE OR ENDANGERED LIST)

Habitat in which bird noted Observed Offshore Residency in air Black rush/ Dwarf Fringe (within Corwen name Scientific name* status space only Saw grass sal t grass mangrove forest Other Laughing Gull icarus aericilla Permanent resident Ring-billed Gull larus delawarensis Minter resident Red-shouldered Hawk BuCeo lineatus Permanent resident Sharp-shined Hawk Accipiter striaeus Minter resident resident .canals Green Heron Butori des seri atus Permanent Glossy ibis Plcgadi s falcinel lus Permanent resident criseata Permanent resident gb Blue Jay Cyanoci Cea American Kestrel Paleo spa rveri us Minter resident Kil deer 1

Charadrius voci ferus Permanent resident Gray Kingbird Tyrannus domini censi s Sumner -resident; Belted Kingfisher Ãcgaceryle alcyon Suamer resident Eastern Headowlark Sturnella magna Permanent resident Ptirms polygloetos Permanent resident gb Hockingbird Red-breaster Herganser plergus scrrator Minter resident Conan ttighthawk Chordcilcs minor Sucmer resident Screech Owl Ocus asio Permanent resident Mhite Pelican Pelecanus erythrorhynchos Minter resident Found dead, only fragments.

'n Bayhead.

Probably seldom lands on South Dade site.

ttomenclature according to Bull and Farrand, l977.

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TABLE 3-2 (continued)

BIRDS FOUND WITHIN OR NEAR THE SOUTH DADE SITE (NOT ON RARE OR ENDANGERED LIST)

Habitat in which bird noted Observed Offshore Residency in air Black rush/ Dwarf Fringe (within Cocmon name Scientific name

• status space only Saw grass salt grass mangrove forest Other iastern Phoebe Sayornis phoebe Minter resident /b /b Black-bellied Plover Pluvialis squatarola Winter resident Yellow-bel lied Sapsucker sphyrapicus vari us Winter resident

/a,b Sanderling Cali dris alba Minter resident Coamon Snipe Capella gallinago Winter resident.

Barn Swallow Hir undo rus Ci ca Migratory visitor Tree Swallow Iridoprocne bicolor Winter resident White-eyed Vireo Vireo griseus Permanent resident I

Turkey Vulture Cacharces aura Permanent resident Blackpoll Warbler Dendroica sCria Ca Migratory visitor /b Palm Warbler Dendroica palmarum Minter resident /b Yellow-rumped Warbler Dendroica coronata Minter resident Horthern Waterthrush Seiurus noveboraccnsis Migratory visitor Cedar Waxwing Bombyci lie cedrorum Winter resident Millet Catoptrophorus semipalmatus Permanent resident House Mren Troglodytes aedon Minter resident /b Downy Moodpecker Picoides pubescens Permanent resident /b

" Found dead, only fragments.

1'n Bayhead.

c Probably seldom lands on South Dade site.

Homenclature according to Bull and Farrand, 1977.

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TABLE 3-2 (continued)

BIRDS FDUND WITHIN OR NEAR THE SOUTH DADE SITE (NOT ON RARE OR ENDANGERED LIST)

Habitat in which bird noted Observed Residency in air Black rush/ Offshore

• Dwarf Fringe Cormon name Scientific name status space only Saw grass salt grass mangrove forest Other Red-bellied Woodpecker Cenrurus carolinvs Permanent resident gb gb Ye 1 1 owl egs Trinya spp. Winter resident Yellowthroat Ceorhlypis erichas Permanent resident a Found dead, only fragments.

In Bayhead.

Probably seldom lands on South Dade site.

Nomenclature according to Bull and Farrand, 1977.

l TABLE 3-3 RARE OR ENDANGERED BIRDS FPUND WITHIN OR NEAR THE SOUTH DADE SITE I 't ln cc not Observed Of/shore Protected cate Residency in air Black rush/ Owarf fringe twithin status s ce onl Sa ress Salt rase man rove forest m Other Scientific name Federal State fCREPA Peregrine falcon raise pereyrinvs Endangered Endangered Endangered liinter resident Brown Pelican Pet ecanuc occiden ca !is Endangered Threatened Threatened Permanent resident SOutnern Bald Eagle ical iaeecus levcocwphalus Endangered Threatened Threatened Pecvcanent resident wood Stork nycceria amecicana Endangered Endangered Rare winter visitor HagnifiCcnt frlgatebird Preface mayniricens Threatened Threatened Permanent resident Osprey Pamiion hcliaevs threatened Threatened . Permanent resident Colvmca levcocc'phaia Threatened Threatened Sucmer resident White-crcnmed Pigeon Leait Tern S cesar el bi franc Threatened Threatened Scsucer resident Roseate Spoonbill Ajija ajaja Threatened Rare Perranent resident Hcngrove Cuckoo Coeeycvs mfnor ThreatenCd Rare Pecccanent resident e Laj 1

Reddish Egret ryrec ea rufescens Percanent resident O w Antillean Ceighthawk Choraei les minor Perrancnt resident rican Redstart Secophcya ruCicilla Race Hlgratory visitor Black. whiskered Vireo vireo aieliolvus Scarcer resident yellow Warbler peIrirniea petechia Rare Pcrrancnt resident Louisiana Waterthrush .eclvrvs rmcavil la Rare Hlgratocy visitor Aeerican Avocet aevurvlroscra americana Special concern Winter visitor Least Bittern irvaryrhvs eriiis special concern lilnter visitor cases.radius ainus Special concern Pervonent resident can~la Cleat Egret cereeca Chvia Special concern Permanent resident canals Snowy Egret svcclcorar nvvcicnrar Special concern Perranent resident canals Black crowned iilghL Heron Creat Blue Heron aracw heresies Specie'I concern Permanent resident canals b I wc rorph y canals white mOrph Permanent resident bV.S. OePartment Of the interiOr. FiSh and Wildlife SerViCC. 1911. Endangered and threatened Wildlife. federal ReglStee'2()36):3642O-36431, JVly 14. 7972 state of Florida, Came and Fresh Water fish Commission. July 1971. Wildlife code of the State of Florida. Chapter 16 E-3. Tallahassee, Florida.

dflorida Committee on Rare and Endangered Plants and Animals. 1976; Inventory of rare and endangered biota of Florida.

Probably seldom lands on South Bade site.

ihrimrted in vicinity of South Bade study area but not observed during this bird survey.

ln Bayhcad,

'iiorenclature according to Bull and Farrand, 1911.

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TABLE 3-3 (continued)

RARE OR ENDANGERED BIRDS FOUND WITHIN OR NEAR THE SOUTH DADE SITE t n r r note Observed .Offshore Protected cate o Residency in ~ ir Black rush/ Owarf fringe (within Scientlfi>> nance Federal State FCREPA status s ace onl Saw ress Salt ress nan rove forest 30 n Other tittle Blue Heron fprerra ceerules Special concerrr Pernanent resident canals Louisiana Heron rlvdranesss tricolor Special concern Perrsanent resident y canals Yellow.crowned Might Heron RycefCorax vrolacea Special concern Pernanent resident White ibis Cudccf sus claus Special concern Perrunent resident y r'anals Black Stirrer Rynchcps nl per Special concern Winter resident Caspian fern Sterne casple Special concern . Minter resident Royal Tern Sterne rMxlsus Special concern Pervranent resident Prairje Warbler oendrclcs discolor Special concern Persranent resident Hairy Woodpecker Plcoldes vlllosus Special concern Pernanent resident Merlin talco coluehsrlus Status tardetervained Minter resident Clapper Ra II Relies lunolroseris Status tardeto rrsined Pervranent resident Stoddard'S Warbler pendrofce dcnlnlce Status

~ rcddsfdl tardeterrelned Minter resident W.S. Oepartnent b State of the Interior. Fish and Wildlife Service. 1977. Endangered and threatened wildlife. Federal Register 42(136):36420-36431. Ju'ly 14 ~ 1977.

of florida. Cane and fresh Mater Fish Cosrsisslon, July 1977. Wildlife code of the State of Florida, Chapter 16 E-3. Tallahassee, Florida.

Florida Cocllttee on Rare and fndangered Plants and Aninals. 1976. Inventory of rare and endangered biota of Florida.

d Probably soldan lands on South Dade site.

f Reported in vicinity of South Olde study area but not observed during this bird survey.

In Bayhead.

Honenclature according to Bull and farrand, 1977.

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study. Red-winged blackbirds and prairie warblers were the most fre-quently observed birds in terrestrial areas. Among the aquatic birds the most common birds along the coast were, in decreasing order, the little blue heron, white ibis, great egret, and snowy egret. In-land from the tidal mangroves, the number of species was reduced and the snowy egret was the most common aquatic bird. The higher diversity and density of birds along the coast reflect the abundance of prey organisms.

Of particular interest to this study are the rookeries of the Arsenicker Keys and Mangrove-Key. An estimate of the numbers of nesting birds was made from counts at the dawn outflights from the rookery. Conservative estimates of the numbers of birds nesting in these rookies were:

~Secies Estimated Population Cattle Egret 2500 White Ibis 1000 Great Blue Heron Little Blue Heron Great Egret 500 total Snowy Egret Loui s i an a He ron Double-crested Cormorant 200 In addi tion to the above species, six anhingas in breeding plumage were flushed from West Arsenicker Key, and reddish egrets, green herons, turkey vultures, and cormorants were noted. A bald eagle nest containing one egg was noted during two consecutive years.

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Three general pathways to feeding grounds were followed by the birds in the Arsenicker Keys rookeries (Figure 3-1 ). The major-ity of the birds flew northwards to Turkey Point where they either continued northward or turned inland and headed northwest. A smaller group left the rookeries and flew inland and northward. A third, much smaller, group flew west or southwest over the South Dade Site'.

Small numbers of white ibises and a very few herons and egrets, possibly less than 10% of the rookery's breeding birds, foraged in the vicinity of the South Dade Site during this study.

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4i BLACK POINT e~ f ') -N-FENDER POIIVT j

HOMESTEAD

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AIR FORCE o' ~" BASE .~." 8/ SCA VIVE L f' L

I 8~V I HOMESTEAD e FLORIDA CITY tI9 I L TURKEY f POIjVT r--~ I C)

~o 6'EST O ARSENICKER KE I yl MANGROVE ARSEIVICKER

)

TURKEY~~ KEY@ 0 KEY POINT MANGROVE COOLING POINT LONG I

~CANALS ARSEIVICKER KEY I D EAST ARSEIVICKER KEY r'o I

I g F.P. 8 L. CARD SOUND

( PROPERTY LIMITS Study r

\ r---- o>>~~co""

LEGEND I ~

J r ~ +POINTops CARD SCALE IN MILES I 0 I 2 W HI T E IB IS O I 2 SCALE IN KILOMETERS I)III CATTLE EGRET gggg OTHER CICONIIFORME S Figure 3-1. Outf1ight patterns from Hest Arsenicker Key rookeries, May 1977.

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3. 3 Marana1 s The small mammal population at the South Dade Site was quantitatively sampled by live trapping at sampling grids located in different vegetation zones. Sampling was conducted every two months for six consecutive days over the course of a year. Larger or scarce mammals were inventoried by observation or indirect evi-dence such as tracks or droppings.

Five species of mammals were trapped during the study and five other species were observed (Table 3-4). The raccoon was .the most wide ranging of the species trapped and showed little preference as to habitat.

Three species of rats were collected during the study. Black rats are excellent climbers and are known to live and nest in trees and bushes. During the study they were found in the saltwater marshes, hammocks, and fringe forest. Cotton rats were found in areas with tall grasses and herbs. These rats are poor climbers and nest in burrows or on the ground. The rice rat is found in a wide range of habitats but prefers cover. This rat is a good climber and swimmer and constructs its nest in shrubs or grasses above the high water level. The rice rat was the most frequently collected mammal.

Populations of cotton rats and rice rats increased with distance from the shore while black rat populations decreased.

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55 TABLE 3-4 MAMMALS COLLECTED OR- SIGHTED IN THE SOUTH DADE SITE AND VICINITY Habitat in whi h ll d ringe Scientific No. trapped Saw- B ac Rus Dwarf Common Name Name during 1-yr stu~ rass Sal t Grass Man rove Forest Shore Rice rat Oryzomys pal ustri s 175 Cotton rat Sigmodon hispidus 85 Raccoon Procyon lotor 58 Black rat Rattus lattus 50 House mouse Hus musculus 1

~Si tlb d:

White-tailed deer odocoileus virginianus Marsh rabbit Sylvi lagus palustris Bobcat Lynx rufus a

Manatee Trichechus manatus Dolphin Tursi ops truncatus a Classified as endangered by U.S. Dept. of the Interior, Fish and Wildlife Service, 1977.

Endangered and threatened wildlife and plants. Federal Register 42(135):36420-36431, July 14, 1977.

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White-tailed deer and deer signs were observed in upland areas west of the present Turkey Point cooling canal system north of the South Dade Site. Marsh rabbits prefer dense cover and were observed mostly in the north and northwest. Bobcats were not seen during the study but numerous sightings have been reported in the area by other observers. The bobcats are believed to be found on the northern and western portions of the FPL property.

Two species of aquatic mammals were noted during the mammal survey. Three Florida manatees, classified as endangered by the U.S. Fish and Wildlife Service, were noted in South Florida Water Management District's canals in the study area. Bottle-nosed dol-phin were noted on two occasions in Card Sound off the eastern bor-der of the property.

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3.4 REPTILES AND AMPHIBIANS Reptiles and amphibians were censused from opportunistic sightings during regular ly scheduled terrestrial and aquatic bio-logical sampling programs. Other species were captured by sweep nets during 36 days of insect sampling. Additions to the census were also made through call identifications made on two night field trips.

The reptiles noted in end adjacent to the South Dade Site were a diverse group that included crocodilians, anoles, turtles and snakes. The species observed in the study area are listed in Table 3-5, and four species of reptiles sighted outside of the study area are given in Table 3-6.

Three species classified as rare and endangered by the U.S.

Fish and Wildlife Service were observed in the vicinity of'he South Dade Site. These species are the American alligator, the American crocodile, and the eastern indigo snake.

Although federally classified as threatened in Florida, the American alligator is increasing in numbers in Florida. The FCREPA has classified the alligator as a species of special concerns 3-18

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TABLE 3-5 REPTILES AND AMPHIBIANS OBSERVED WITHIN THE SOUTH DADE SITE Habitat in which noted Black rush/ Dwarf Fringe Cottuen name Scientific name* w rass Salt rass man rove Forest REPTILE Bark Anole anolis distichus Green Anole anolis carolinensis carolinensis Brown Anole anolis sagrei Corn Snake Elaphe guttata gutcata Eastern Diamondback Rattlesnake Crotalus adamanteus Eastern Indigo Snake Drymarchon corais couperi Florida Water Snake Natrix -fascia ta pictiventris Hangrove Water Snake Natri x fascia ta conpressicauda Everglades Racer Col uber constrictor pal udicola AHPHIBIAN Florida Cricket Frog Rcris gryllus dorsalis Greenhouse Frog Eleutherodactylus planirostris planirostris Pig Frog Rana grylio Southern Leopard Frog Rana utricularia Cuban Treefrog Nyla septentrionalis Green Treefrog Nyla cinerea a

Classified as a species of special concern by Florida Connittee on Rare and Endangered Plants and Animals. 1976.

Inventory of rare and endangered biota of Florida.

Nomenclature according to Conant, 1975.

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TABLE 3-6 REPTILES SIGHTED OUTSIDE OF SOUTH DADE SITE L-31-E Sea-Dade Borrow Interceptor Common name Scientific name* Canal Canal Ditch American Al 1 i gator ajli gator missi ssi ppi ensi s AmeriCan CrOCOdile Crocoayius acutus Water turtles Chrysemys Spp.

Florida Softshell Tri onyx ferox

> Classified as threatened in Florida by the U.S. Department of the Interior, Fish and Wildlife Service. 1977. Endangered and threatened wildlife and plants. Federal Register 42(135):36420-36431, July 14, 1977.

Classified as endangered by U.S. Department of the Interior, op. ci t.

Nomenclature according to Conant, 1975.

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Alligators prefer freshwater wetlands, so much of the study area is marginal for this species due to saline conditions. however, small numbers of alligators may occur almost anywhere on the FPL property. The most suitable habitat in the study area for alli-gators is the saw grass zone and the adjacent canals. The total number of alligators on the FPL property appears small and the study area contains limited alligator habitat.

The American crocodile is classified as endangered on both the FCREPA and federal lists, and is considered endangered through-out its total range. The FPL property is within the historical and present range of the American crocodile. They have occasionally been see along the mainland shoreline of southern Biscayne Bay, Card and Barnes Sounds, in the borrow canal of Levee 31-E, and in the Sea Dade Canal on and adjacent to FPL property. Crocodiles appear to be attracted to man-made canals and borrow pits because they prefer deep, quiet-water sites.

A minimum of 3 adult-sized crocodiles (2 m or larger) were at least seasonal residents along the north-south leg of the Interceptor Ditch during 1975 and 1976. A dead juvenile (25 cm) was found during September 1976 in the adjacent western-most cooling canal.

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The eastern indigo snake, which occurs throughout peninsular Florida, has been reported from the saw grass zone of the FPL prop-erty. This snake is generally an inland species that does not utilize brackish water habitats. Therefore, most of the South Dade study area is marginal habitat for this snake.

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gualitative fish surveys were conducted bimonthly to determine the kinds of fishes present at the South Dade Area and the habitats with which each species is associated.

The composition of fish populations is influenced by many factors such as water depth, salinity, temperature, and bottom cover.

Restrictive chemical factors include low oxygen levels in the plugged canals and high salinity levels on hypersaline flats. Under these conditions, entire populations at times are restricted to a single species. Nevertheless, the fish of the study area wetlands may occur in sufficient numbers to be the most important food resource in an otherwise impoverished aquatic environment.

Twenty-four species of fish were collected at the South Dade Area and four additional species were observed. Table 3-7 lists the species noted and the habitats in which they were found.

Use of these habitats is often seasonal. During the dry season the inland areas are dry, with the exception of scattered ponds. During the wet season, however, these areas often support relatively large populations of sma'll fish.

The most commonly netted fishes, and probably the most import-ant in terms of their place in the food web, were the mosquitofish, 3-23

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TABLE 3-7 FISHES COLLECTED AND OBSERVED AT THE SOUTH DADE AREA Mabitat in which noted Tidal creeks c>,~ c~ co d

o+~ ee ~+ N+ c". oc

~C ,c, e+ q c+ co + +

Conmon name Scientific name Great Barracuda Sphyraena barracuda Pygmy Fi lefish Bonacanchus serifer n Canbusia rhizophorae found occasionally in tidal creeks Hangrove Hosquitofish Bluestripe Grunt Haemulon sciurus Crested Goby . tophogobius cyprinoides Crevalle Jack Caranx hippos Ki llifish Fundulus Sp.

Oiamond Killifish adinia xenica Goldspotted Ki llifish Floridichrhys carpio Rainwater Ki llifish sucania parve Sheepshead Hinnow Cyprinodon variegaeus Hojarra zucinosromus spp.

Sailfin Holly Poecilia laripinna Hosquitofish Card>usia affinis Mullet Bugil sp.

Redfin tteedlefish Serongylura norara ie t reatene t on ttee on are an n angere ants an noma s, nventory n rare an en angere iota ass) as y e a Comm of Florida.

ttomenclature according to Bailey, et al., 1970.

m m m m m m m m m m m m m TABLE 3-7 (continued)

FISHES COLLECTED AND OBSERVED AT THE SOUTH DADE AREA Habitat in which noted Tidal creeks Cp Cp

~e b ~Q ~C' QC c+ < ck <o o~~ 4' c~

ee~ w+ e~ oc Comnon name Scientific name " 4~ ~ c~ a~ f, +

Pinfish Cagodon rhonboidcs Pipefish Sygnathus Sp.

Checkered Puffer Sphoeroidcs testudineus Blue Runner Caranx crysos Schoolmaster tutjanus apodus Hardhead Silverside ntherinoxorus stipcs Smalltooth Sawfish pristis pcctinata Sharks Elasmobranchs Gray Snapper Lutjanus griseus Snook Ccntropomus undccinaiis Southern Stingray Dasyatis aneri cane Tarpon Hegalops atiantica Gulf Toadfish Opsanus beta a Classified as threatened by the Florida Comnittee on Rare and Endangered Plants and Animals, 1976. Inventory of rare and endangered biota of Florida.

• Nomenclature according to Bailey, et al., 1970.

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rainwater killifish, hardhead silverside and mojarras. These fish are fed upon by larger carnivorous fishes and wading birds.

No species of fish currently listed as threatened or endan-gered on any federal or state list is known to occur within 50 miles of the South Dade study area. The mangrove mosquitofish, which was found occasionally in tidal creeks in the South Dade study area, is classified as threatened by the Florida Committee on, Rare and Endangered Plants and Animals (FCREPA). This species is restricted to red mangrove areas and in Florida it occurs commonly in tidal creeks with good water movement.

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3. 6 SELECTED INVERTEBRATES 3.6.1 Soil Macroinvertebrates guantitative soil samples were taken at terrestrial stations in representative habitats to determine the kinds and abundance of soil macroinvertebrates in the South Dade Area. Underwater sites were sampled with a Ponar dredge. Most macroinvertebrates were found within 20-30 cm of the surface. Table 3-8 lists the species of soil macroinvertebrates and the habitats in which they are found.

Although a representative range of substrates were sampled in each area, the number of soil macroinvertebrates collected was generally small. The exception was in the fringe forest where a large number of annelid worms were collected at the banks of the creeks. The fringe forest yielded the largest number of species and individuals.

Surface and Arboreal Molluscs Surface and arboreal molluscs were inventoried at each of the stations used for soil macroinvertebrates. Five species of surface and arboreal molluscs were collected (Table 3-9). Four of the five species were collected from the ground in the dwarf mangrove zone and in the fringe forest zone. These molluscs are primarily herbi-vores and detritivores and are fed upon by numerous wading birds and raccoons.

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TABLE 3-8 SOIL MACRO INVERTEBRATES COLLECTED AT THE SOUTH DADE AREA Habitat in which noted Saw Black rush/ Dwarf Fringe Common name Scientific name rass Salt rush mangrove forest Sea scud Gammarus fasciatus Ribbon worms Lineus Sp.

Amphi porus i mpari spi nosus Amphi porus Sp.

Flat worm Mgremeci plana elegans Centipede Geophilus umbracticus Sow bug onisci us asselus Pill bug Cgaethura cari nata But terfly (pupa) Lepi doptera Fly Geosargus Polychaete worms Cirratulus Sp.

Nereis pelagica Nerei s li mnocola Nereis SP.

Harphgsa bella" Narphgsa lei dpi Arenicola cristata Terebellidae 01 i gochae te worm . Tubificidae 3-28

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TABLE 3-9 SURFACE AND ARBOREAL MOLLUSCS COLLECTED AT THE SOUTH DADE AREA Ha itat sn whic noted Saw Black rush/ Dwarf Fringe Common name Scientific name* grass Salt rass man rove forest Ladder horn shell Ceri thedi a seal ari formi s Coffee melampus Melampus coffeus Common crowned conch Melongena corona Angulate periwinkle -Li ttorina angulifera Florida marsh clam Polymesoda mari tima

• Nomenclature according to Abbott, 1974.

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3.6.3 Insects and S iders Insects and spiders were collected for three consecutive days and nights every two months at stations in representative habitats.

Insects were collected during the day using specialized nets for both aerial and vegetation sweeps. Collection techniques were standardized,so that comparisons of relative abundance could be made.

Insects were collected during the night using a CDC miniature light trap. During the initial night trapping session, three locations were selected within each sampling site for the purpose of achieving representative samples.

The 139 species of insects, 36 spiders, and 8 other arthro-pods collected are listed in Table 3-10 by the habitats in which they were found. Seasonal changes in diversi ty and number of individuals were seen in both day and night collections. During the dry month of April 1975, the light traps generally yielded fewer than 10 animals.

With the onset of summer and the rainy season, there were, increases of up to three orders of magnitude per trap-night. As is generally the case with summer insect populations, the dipterans were responsible for this marked increase. Hosquitos were the most numerous dipterans.

The most common mosquito in the area was the salt-marsh mosquito, Aedes taenia ozhgnchus.

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TABLE 3-10 INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in whic note Saw ac rus / Dwarf Fringe Common name Scientific name rass Salt rass man rove forest INSECTS Plant hopper Acanalonia Sp.

Slant faced grasshopper Acridinae Short horned grasshopper Zeptysma margi nicolli s Romalea microptera Paroxga clavuli ger Sebi stocera obscura Stenacris Sp.

S tenacri s vi teri penni s uni den ti fi ed s p.

Dame rs Aeshni dae Flea beetles Al ticinae Drug store beetle Anobi i dae Flat fungus beetle Aradidae Bees Zylocopa Sp.

Apis m lli fera Owl fly Ascalaphidae Robber fly As i l i dae Gi ant waterbug Lethocerus grise us Roaches Latiblattel j.a rehni (?)

Cari blatta SP.

unidentified sp.

Aglaopteryx Sp.

Braconids Braconidae

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TABLE 3-10 (continued)

INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in whic note Saw ac rus warf Fringe Common name Scientific name* rass Salt rass man rove forest INSECTS (continued)

Ground beetle Poeci lus l ucublandus Agon um docorum f

uni denti ied sp.

Wood borer Elaphidion

'ucronatum

(?)

Spittlebug Prosapa bi cincta unidentified sp.

Chal cid Chalcididae Moths Cosmopterygidae Ni dge Chronomidae Lace wing Chrysopa Sp.

Leaf hopper Cicadellidae Cixiidae Mealy bugs Pseudococcus sp.

Tea scale Forinatheae Ladybird beetle Ceratonegi lla maculata Narrow winged damsel fly Ischnura ramburi unidentified sp.

Beetles Bostrichidae Chrysomel i dae Lagriidae (?)

Scarabaeidae (?)

unidentified sp.

Mosquito Aedes taeni orhI jnch us Anophel es Culex unidentified sp.

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I TABLE 3-10 (continued)

INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in whse note Saw ac rus / warf Fringe Common name Scientific name rass Salt rass mangrove forest INSECTS (continued)

Snout beetle. Curculionidae Flies Di ptera Mycetophi 1 i dae Doli chopodidae Muscidae Cecidomyidae Ceratopogonidae unidentified sp.

Long-legged flies Dol i chopodi dae Click beetle El ateridae Shorefly Ephydridae Pl anthopper Flatidae Ants Camponotus herculeanus I unidentified sp.

Planthoppers Acanaloni a Sp.

Ful gori dea No common name Gasteruptiidae Measur ing worm Geometridae Water striders Gerridae Whirl i gi g beetle Dineutus Sp.

No common name camptonocus caroli nensi s 3-33

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TABLE 3-10

('continued)

INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in whic note Saw ac rus / warf Fringe Common name Scientific name* rass Salt rass mangrove forest INSECTS (continued)

Crickets Remobui s Gryllus Crit oxi pha unidentified sp.

Mining bees Hali ctidae Pl ant beetle pti 1odactyla angustata Bugs Miridae (?)

unidentified sp.

Ski pper Hesperiidae Scale insect Coccidae unidentified sp.

Water scavenger beetle Hydrop hi 1 i dae Yellow faced bee Hylaeinae Ichneumons Rhyssella Sp.

unidentified sp.

Termites Isoptera Butterf1 i es, moths Lepidoptera Liparidae (?)

Ge 1 echi i dae Grass fly Leptogastridae Common skimmers pachgdiplax longipennis/

Libellula Sp.

sp. v'nidentified 3-34

I TABLE 3-10 (continued)

INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in which note Saw ac rush/ Dwarf Fringe Common name Scientific name* rass Salt rass mangrove forest Gossamer-winged butterfly Lycaenidae ( ?)

Seed bugs Lggae us Man ti ds Thesprotra grani nis Gonatista gri sea v'hanti Stagnvmanti s carolina uni denti fied s p.

Mantid flies spa Leaf cutting bee Megachi 1 i dae Fl annel moth Megal opyge operculari s No common name Megal opygi dae Blister beetle zpicauta sp.

Cotanon fly Muscidae Brush-footed butter fly Danaus plexi ppus unidentified sp.

Dragonfly Odonata Stink bugs Pentatomidae Walking stick Ani somorpha buprestoi des unidentified sp.

Ambush bug Phymatidae Sul fur butterfly Pieridae Mealy bugs pseudococcus Sp.

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TABLE 3-10 (continued)

INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in whic note Saw ac rus Dwarf Fringe Common name Scientific name* rass Salt rass man rove forest INSECTS (continued)

Bagworm Thri doptergx ephemeraeformi

'Assassin bug Reduvi idae Flesh fly Sarcophagidae Io moth Autom ris io Fungus gnat Sciaridae Engraver beetle phthorophloeus frontalis (?)

Shield back bug Scul tel 1 eri dae Solitary wasp Chlorion Sp.

unidentified sp.

Flower fly Syrphi dae Horse, deer, fly Chrysops Sp.

Tabanus sp.

No common name Taehinidae (?)

Crane flies Ri pul i dae Pygmy grasshopper Parati tti x rugosus TI Katydid Microcentrum Sp. (?)

Orcheli um sp. (? )

Mi crocentrum rhombi foji um (?)

un i den ti fied sp.

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TABLE 3-10 (continued)

INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in whic note Saw ac rus / warf Fringe Common name Scientific name rass Salt rass mangrove forest INSECTS (continued)

Caddi s fly Trichoptera Hydropti 1 i dae unidentified sp.

Cri eke ts Crytosipha 'p.

Paper wasp Pol istinae Polistes Sp.

unidentified sp.

SPIDERS White eyed spi der Ti tanoeca americana spider Clubionidae Aniphaenidae unidentified sp.

unidentified sp.

Araeneae Orb spider Cyclosa Sp.

Argi ope aurantia Verrucosa Sp.

Gasteracantha li el psoi des Zeucauge venusta Argiope araentata Acanthepei ra stel j.ata Argiope SP. (?)

Araneus Sp.

Mecynogea lemni sea ta Eustala Sp. (?)

Nephi la clavi pes unidentified sp.

Hunting spider Gnaphosidae Sheet-web spider Linyphilidae (?)

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TABLE 3-10 (continued)

INSECTS COLLECTED IN THE SOUTH DADE AREA Habitat in which note Saw B ac rus / Dwarf ringe Common name Scientific name rass Salt rass mangrove forest SPIDERS (contInoed)

Wol f spider Pardosa sp, Zycosa sp, unidentified sp.

Spider-hunting spider pro'sp.

Nursery web spider Pi saurina, mi ra

-Dojomedes sp.

Jumping spiders'entzia sp.

Phi di ppus audax Peckhamia pi cata Metacgrba undata Marpi ssa pikei unidentified sp.

Four jawed spiders Leucauge Sp.

Tetragnatha straminea Cob-web spider Argyrodes elevatus OTHER ARTHROPODS Scud Amphipoda Scorpions Centruroides gracilis Centruroi des hentzi Centi pedes Geophilomorpha Sp.

l Arenophi us S p.,

I Pill bugs Ligia Sp.

-unidentified Tick Amblyomma maericania 3-38

I Generally, the summer season yielded the greatest abundance and diversity of insect life. Numbers of insects and spiders corre-lated with plant diversity due to the increase in ecological niches.

Values of the mean, standard error and range of diversity were plotted against month of collection (Figure 3-2). The mean species diversity in the fringe forest over the course of the year was consistently less than one. This low diversity was due, in part, to the small numbers of niches afforded by an almost homogeneous plant community. Also, tidal inundations precluded ground forms. During August, species diversity declined in all zones except the saw grass zone which showed the highest species diversity for the year. During October, while the saw grass zone showed a slight decline, all of the other zones showed a clear increase in diversity. It is probable that maximum breeding success occurred in the saw grass zone in August.

Dispersion from the saw grass into the other major zones resulted in a secondary diversity peak in the more saline areas in October.

'I Figure 3-2 shows that the greatest mean diversity occurred during April in all but the saw grass zone. This indicates that perhaps more niches are available in these zones during the winter-spring dry season. Peak insect diversity corresponds with important bird nesting seasons. Many birds depend solely on insects for food or shift to an exclusively insect diet during breeding season.

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fl CD o.so SAW GRASS ZONE I

i.oo C/)

)

OC LU O.SO I~

BLACK RUSH/SALT GRASS ZONE l.o 0 C/I

)

M O,SO lm DWARF NNGROVE ZONE I

Coo C/s

)

cs:

UJ oso FRINGE FOREST ZONE Figure 3-2. Diversity of day insect collections (mean, range and standard error),

South Dade Area.

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No rare or endangered insects, spiders, or other arthropods were collected or noted in the South Dade Area.

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Zooplankton is a major part of the food chain linking the South Dade Area to the Card Sound ecosystem. Zooplankton feed on detritus, phytoplankton, and other zooplankton. As the zoo-plankton is flushed from the estuaries, it becomes food for other animals such as invertebrates and fish. Zooplankton samples were collected monthly using a bilge pump fitted with a wide-mouth funnel to minimize avoidance.

A list of the zooplankton groups collected at the South Dade study area and their relative abundance in various habi-tats is given in Table 3-11. Copepod crustaceans were the most important component in the zooplankton. In general, the concentrations of copepod nauplii decreased in the direction of mouth and embayment stations because salinity values were higher seaward. Acm Cia tonsa, one of the most important copepods in Biscayne Bay and Card Sound, predominanted in near-shore areas. A. tonsa tolerates very low salinities and achieves maximum production at a salinity about one-half that of seawater (Barlow, 1955). Therefore, it appears the A. fossa in Card Sound and Little Card Sound is supplemented by copepod production 3-42

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in lower salinity tidal creeks. Peak copepod production usually occurred in September when wet season conditions caused low salinities.

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TABLE 3-11 ZOOPLANKTON GROUPS COLLECTED AT SOUTH DADE AREA AND THEIR RELATIVE ABUNDANCE BY HABITAT (A=abundant; C=common; 0=occasional) i a ree s Plugged Open Saw Black Rush/ Dwarf Mi d- Embay-S ecies or Grou canal canal rass salt rass man rove Source creek Mouth ment CRUSTACEANS Copepods Nauplius Harpacticoid copepodite Calanoid copepodite Cyclopoid copepodite Harpacticoid adult Calanoid adult Ostracods Naupli us Adult Cladocerans Adult Decapods Zoea 0 Barnacles Nauplius ROTI FERS Adult ANNEL IDS Polychaeta 1 arvae lSLLUSKS Gastropod veliger Pelecypod veliger TUNICATES Larvacean

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3.6.5 A uatic Molluscs Molluscs were sampled every two months by Ponar Dredge at sampling stations located in representative habitats throughout the South Dade study area. A list of the mollusc species collected in the study area is presented in Table 3-12.

The 36 molluscan species collected in Ponar Dredge samples are typical members of subtropical seagrass or mangrove habitats.

These species exhi bit a wide range of salinity tolerances and are found from marine to brackish environments. The highest diversity of molluscs was found at the creek mouths.

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TABLE 3-12 AQUATIC MOLLUSCS COLLECTED WITHIN THE SOUTH DADE AREA Habitat in which noted Tidal Creeks 81ack rush/ Dwarf Fringe Plugged Open Ni d-Coo+on name Scientific name* Saw grass Salt grass mangrove forest canals canals Source creek Youth Embayment Adam's ark arcopsis adamsi Variable bittium Diastona varium Channeled barrel-bubble acteocina canali cuiata Striate bubble Bulla striata 8road-ribbed cardita Cardi tanera fioridana f or i da 1 marsh clan polynesoda nari tiru Horse conch Pieuropioca yi yantea Cross-barred chione Chione canceilata Coffee-bean snail Helanpus coffeus Atlanta cyclinella Cyclinella teni us Greedy dove shell anachis avara Gem shell Gems yemen Black horn shell Bati iiaria niniau Dotted horn shell Ceri thiun nuscarum Ribbed horn shell Cori thidea scaiariformi s Homenclature according to Abbott, 1974.

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TABLE 3-12 (continued)

AQUATIC MOLLUSCS COLLECTED WITHIN THE SOUTH DADE AREA Habitat in which noted Tida Creeks Black rush/ Dwarf Fringe Plugged Open Nid-Corrrnon name Scientific name* Saw grass Salt grass mangrove forest canals canals Source creek Youth Embayrrznt File keyhole limpet zucapinella limatula Striped false limpet slphonaria pectinata Little white lucine codakia orbiculari s Harginella Harginclla apicina Atlantic modulus Nodulus modulus Conrad's false mussel rrytilopsis lcucophaeata Scorched mussel Brachidontes exustus Tulip mussel ra>diolus armricanus Virgin nerite Neri tina virginea Adele's dwarf olive olivclla adclac Southern periwinkle bfttorina anyulifcra Caribbean risso Rissoina bryerca Smooth risso Zcbina brovniana Florida rock-shell Thais hacmastoma floridana Spotted slipper shell Crepidula maculosa Nomenclature according to Abbott, 1974.

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TABLE 3-12 (continued)

A(VATIC t'tOLLUSCS COLLECTED WITHIN THE SOUTH DADE AREA Habitat in which noted ada Creeks Black rush/ Dwarf Fringe Plugged Open- Hid-Cordon name Scientific name* Saw grass Salt grass mangrove forest canals canals Source creek Youth Embayment Conrad's transennella rransennella conradina Da'l 1's turboni lie l rurboni la dal li Stellate turrid Bancelia srellara Pointed venus anortal oca rdi a a uberiana Hottled dog whelk Nassarius vibex Trellis wentletrap Epi roni um lanel losum

• Nomenclature according to Abbott, 1974.

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3. 7

SUMMARY

The South Dade Area is unsuitable to the large wading birds as a rookery or nesting area. Egrets, herons, storks, and similar forms prefer. as nesting areas small islands, such as the Arsenicker Keys and Mangrove Key, or dense wooded areas with tall trees. The South Dade Area lacks the security of tall trees and the water barrier'ffered by islands. Although it is possible that the wading species might nest on the site, the easy access by predators renders it marginal. Field data from several consecutive years. confirm the absence of rookeries on the South Dade Area. The area is used, however, as a feeding ground and forage area for an estimated 10Ã of the Arsenicker Key rookery.

The South Dade Area provides an excellent habitat for rice and cotton rats, black rats, and raccoons. All are common and, in some instances, are considered nuisance species. Deer, rabbit and bobcat were occasionally observed'. With the excep-tion of manatees in adjacent South Florida'Water Management District canals, no rare or endangered mammals were observed on the South Dade Site.

The American alligator and American crocodile, both considered rare and endangered in Florida by the U.S. Department of the Interior, were observed near the South Dade Area.

3-49

As compared with upland, drier habitats found in south-eastern Florida, the South Dade Site is marginal for the snakes and turtles common to the region.

Fish studies provided about 30 taxa, all relatively common to estuarine habitats. With the exception of the mangrove mosqui-tofish (listed by the Florida Committee on Rare and Endangered Plants and Animals), no endangered fishes were observed. The tidal creeks and fringe forest areas of the South Dade Area are considered excellent feeding and forage areas for nearshore fish species. The remainder of the area may at times-provide good habitats for salt-tolerant and fresher water small fish species; however, the majority of the area has insufficient water most of the year to support fishes.

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4.0 EXPERIMENTAL STUDIES

4.1 INTRODUCTION

Experimental studies were performed at the South Dade Area to determine the vegetation peak standing crops, the effects of soil characteristics on plants, nutrient turnover in salt marshes, and the possible influence of groundwater seepage on mangrove eco-sytems. These studies were relatively complex, and required an understanding of both energy and nutrient flux within the ecosystem.

The best approach was to reduce the task to easily-identified com-ponents within the ecosystem, from this derive a composite of the parameters and produce a reasonably cohesive picture.

The conceptual approach to determining the productivi ty of the ecosystem was to measure how much energy or material entered the system, how much remained, and how much was transported for use elsewhere. Vegetative material in the form of peak standing crop provides an estimate of productivi ty, or at least carrying capaci ty, of a habitat, The more mobile, and therefore transient,,animal components of a habitat are excluded. Standing crops information, however, does not provide any insight as to the rate of vegetative production. This rate must be measured in terms of organic carbon productivity, or how much carbon is "fixed" or incorporated within the ecosystem. Organic carbon, found in living and dead plant and animal tissues, returns to the nutrient pool following death and decay of plant products'-1

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How organic carbon and nutrients were transported from one habitat to another required examination of the transport mechanisms available to export particulate and dissolved substances into adjacent Card Sound. Water, both from rainfall runoff and cyclical hydraulic fluctuation caused by tides,was the principal mechanism.

Elucidation of water's role in transport required a thorough under-standing of tidal amplitudes which control the volumes of water washed in and out of the habitat (see Section 4.4.2: Hydraulic Studies).

4.2 VEGETATION PEAK STANDING CROPS Estimates of vegetation peak standing crops were made to identify the vegetative components of the ecosystem that contribute to the overall plant biomass of the area. After the standing crop of individual plant species which inhabit the area is measured, some determination as to the relative importance of each species may be made. Relative importance is a subjective evaluation, based upon I

site study data, of the amount of material each species can make available to the ecosystem. This material, in the form of roots, leaves, wood, and other litter products, can then be analyzed for nutritive value.

4.2.1 Nethods In order to describe vegetation peak standing crops on the South Dade study area, several low-level aerial surveys were made.

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Vegetation zones were delineated through interpretation of several infrared photographs of the study area. The quantitative vegetation analysis was performed along a 3700-m study transect (Figure 4-1) which extended from a point on the Model Land Canal southeast to Card Sound. To determine biomass by means of destructive sampling, off-transect. study areas were identified and used to prevent the sampling from having an effect on the processes under study along the transect.

Study parameters included species densities and areal coverage, vegetative biomass, leaf morphology, and dwarf mangrove population structure.

4.2.2 Results S ecies densities and areal covera e A point-grid analysis of the area represented by each of these vegetative components resulted in the values given in Table 4-1.

Although major vegetation zones have been identified and areal coverages computed in terms of hectares and percentages, it must be clearly understood that vegetation zonation is a gradual blending of different plant species from one habitat into another. Mangrove species are particularly well adapted to all of the habitats and salt regimes at South Oade; consequently they appear in all habitats, but in various amounts. Table 4-2 demonstrates the various densities by habitat. Red mangroves occur at all station locations; however, 4-3

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M W W

~(jr 6 P" I 4l arlseI.T. Stat'tl 1UCa 1Qt"IS l)dd r,embers have beer. de;eted due :o space t tg COIISIItBrht;lo!JS.

( I om I

pan~

~~QB c +2k

'r'

/Y Little Card 5ouna

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TABLE 4-1 VEGETATION TYPE AND AREAL COVERAGE OF MAJOR ZONES OF THE SOUTH DADE SITE Percent Ve etation t e Hectares(Acres) Covered Fringe forest 142.0 (35l) 3.3 Dwarf mangrove 1304.0 (3222) 30.7 Black rush/

salt grass 424.4 (1049) 10.0 Saw grass 1630.3 (4028) 38.3 Saltwater hammock 264.8 (654) 6.2 Freshwater hammock 488.1 (1206) 11. 5 Total 4252.5 '(10508) 100.0 4 5

) i TABLE 4-2 DENSITY OF MANGROVE SPECIES (INDIVIDUALS/m ) ALONG THE SOUTH DADE STUDY TRANSECT Station Red man rove Black man rove Mhite mangrove 2 0.02 0.06 0.30 8 0.02 0.01 4.03 16 0.01 0.01 1.08 23 2.17 0.14 0.38 30 3.72 37 3.17

• The omission of values for the density of black mangrove and white mangrove below Station 23 indicates their absence as a significant component of the vegetation. Although black mangrove is occasionally found below Station 23, the frequency is too small for meaningful density measurements.

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the number of individuals per square meter changes from 3,17 to

0. 02/mz.

Ve etative Biomass The above-ground biomass measurements of vegetation showed the distribution to be in both horizontal and vertical directions.

These measurements were taken at randomly selected, off-transect sites in each of the vegetational zones and the saltwater hammock.

Biomass harvest data in the dwarf mangrove zone are given in Figures 4-2 and 4-3. The red mangrove was clearly the dominant bio-mass component in the dwarf mangrove zone, comprising over 98% of the total above-ground biomass. The two components that accounted for the majority of the biomass were wood and proproots, comprising 44% and 35.5! of the total, respectively. The characteristic struc-ture of the scrub mangroves was reflected in the distri bution of the leaf biomass. The leaves were usually contained in a narrow band between 0.5 and 1.0 m above the ground surface. Again, as shown in Figure 4-3, the red mangrove was the predominant contributor to both leaf biomass and area, providing 97% of the total leaf biomass and 95% of the total leaf area.

I

'he data obtained indicated the leaf biomass for the crown of the red mangrove was 138 g/m and the leaf area was 0.23 mz/mz.

The biomass measurements were then used to calculate the total biomass 4-7

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BIOMASS BY COMPONENT 1.0 CI 4/

C)

I/I VI

)

4I 4I I

OC I

4l K 0.5 4I C) cC 4I 0 200 4 0 6 8 BIOMASS (B/m~)

BIOMA'S BY SPECIES 1.0 C'I 4I CO OC 4I CS 4I I

4I I

Vl I

CC I

I4 VI Vl I/O I/l 4I I Vl III Vl VI 4I OC I

CI 4I CC 200 4 0 6 BIOMASS (B/m.)

Figure 4-2. Distribution and biomass of dwarf mangrove zone by component and species.

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LEAF BIOMASS 1.0

)

CCC CC O

CCC CCC

)

CCC O W O

I

<<C C/C CD CC.

O C<<J W hC CC: V 0 10 20 30 40 50 BIOMASS (g/m~)

I.EAF AREA 1.0 C<<C O

CL CD CCJ CXi C/C I R NC/C O W C/C C<<j ~ C: C/C Q

OCC: CD CX CD O

LU CC:

0.05 0.10 0,15 0.20 AREA (m:/ m )

Figure 4-3. Leaf biomass and leaf area in the dwarf mangrove zones..

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of dwarf mangroves in each of the vegetative zones containing dwarf mangroves. Black mangrove biomass was estimated by determining a typical structure for a scrub black mangrove and multiplying by the number of individuals in each zone as determined by area-density relationships. The biomass of white mangroves was calculated in the same way as that for the red mangroves.

Figures 4-4 through 4-7 summarize the results of biomass deter-minations representative of the black rush/salt grass zone of the South Dade study area. The red mangroves, also present in the black rush/salt grass zone, were the largest contributor to the total biomass in the black rush/salt grass zone studies. This was primarily due to the amount of woody structures. A transition in the gross structure of both black rush/salt grass sites was observed in the distribution of biomass, especially the photosynthetic leaf biomass. A comparison of Figures 4-3 and 4-5 indicates that most of the photosynthetic structure in the dwarf mangrove zone was found above 0.5 m, while the major portion of the photosynthetic structure of the black rush/salt grass was below 0.5 m. An increase in both the detritus and white mangrove components was seen in the black rush/sal t grass zone as compared with the scrub mangrove zone. Assuming that these sites were representative of the standing crop of black rush on the South Dade property, the total biomass can then be estimated. The results of these estimates are given in Table 4-3.

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BIOMASS BY COMPONENT 1.0 Cl LO LLJ ILJ Vl

~ 0.5 LJL LLJ LO Cl CI LLJ LJI LLJ CO '/I LLJ

)

IJI LLJ a

LLJ I

OO I

LLJ CI 0

0 200 400 600 BIOMASS (g/m~)

BIOMASS BY SPECIES 1.0 I

)

LJI LLJ Cl OO LO 5

OO Ci hC LLJ a

OO I

= 0.5

)

LJL I VI

)

IJL iil Cl OO

~ O I

OO I

LLJ LJJ Cl I Cl OO hC 0

0 200 400 600 BIOMASS (g/m.)

Figure 4-4. Distribution of biomass in black rush/salt grass zone by component and species.

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LEAF BlOHASS ICJ C)

CIC I/I C9 CC:

CC.'i C)

I 0

I/C g

~ v I/I I

ct I/O 5

CC hC CCI 0

0 100 200 BIOMASS (g/m~)

LEAF AREA 1.0 ICC la>

I CC!

CC; III CC I/O 5

hC CCI I/I C/I 0 0.5 1.0 1.5 AREA (m*/m-)

Figure 4-5. Leaf biomass and leaf area in black rush/salt grass zone.

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BIOMASS BY COMPONENT 1.0 W

C/C O 3

CC; CD I

C/C C/C O

R D Vl 8 D. Ch D CCC CL C/C

~~ 05 CCJ O

I

)

CD CCC O

O O IW CCJ O

C/C 0 200 400 600 BIOMASS {g/m2)

BIOMASS BY SPECIES 1.0 C/C C/l lU I O

OC C/C CD s 5

CY O

LCC 5C E 0.5

)O C//

CD CX I

C/C 8

CC.

Cij O

CD 0

0 200 400 600 BIOMASS {g/m )

Figure 4-6. Distribution of biomass in black rush/salt grass zone by component and species {off transect).

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~

gi

LEAF BiOMASS 1.0 I<<J I

)

W O CC I/l l

O Ial CC S

<<C Kl l )

M O

I/l CD I/l CC le CC LJ Cl 0 100 200 300 BiOMASS (g/m>)

LEAF AREA 1.0 W

)O 4J CC CD l ID Q O I/I I<<J I

I/I O CC I<<l g IV I

lC I/I CD m 0.5 I/I I<<I l

O

<<C I/l CD O

CC lC O

0.5 1.0 1.5 2.0

""EA (m /m )

Figure 4-7. Leaf biomass and leaf area in black rush/

salt grass zone (off transect).

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TABLE 4-3 BIOMASS ESTIMATE OF 424.4 HECTARES (1049 ACRES)

OF BLACK RUSH ON THE SOUTH DADE AREA 2a Com onent /m Metric tons Live black rush 80.5 341.8 Dead black rush 130.0 551.7 Total 210.5 893.6 a

Dry weight at 70'C.

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The sharp delineation between the black rush/salt grass zone and the saw grass zone was indicated by the biomass harvest in this habitat. Figures 4-8 and 4-9 show that, except for a slight amount of salt grass, the saw grass zone was solely composed of above-ground detritus and saw grass. Table 4-4 shows the total biomass of saw grass on the south Dade area.

An examination of Figures 4-4 to 4-9 reveals several trends.

Perhaps thy most obvious is an increase in the relative abundance of detritus as a component of the total biomass as one approaches the saw grass zone. In the scrub mangrove zone, detritus represented only 1.6/

of the total organic structure (above ground), but in the saw grass zone, it increased to 51.6Ã of the organic structure. Another trend is seen in the relative increases in both leaf biomass and leaf area from the lower to the upper zones of the transect. The scrub mangrove zone averaged 70.35 g dry weight of leaves per mz of ground surface, repre-senting 8.9K of the living biomass . This is contrasted with the black rush/salt grass and saw grass zones, where the photosynthetic structures comprised 52.1/ and 48.4X of the living biomass, respectively. Leaf area also increased in the upper regions of the study property. The leaf area of the scrub mangrove zone averaged 0.24 m of leaf surface per m of ground surface. This increased rapidly to 1.65 mz/mz in the black rush/salt grass zone, and 2.03 mz/m". in the saw grass zone. A summary of the biomass distribution calculations for the major vege-tative components of the South Dade study area is given in Table 4-5.

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BIOMASS BY COMPONENT 1.0 C/I CCI Cll I

0 5 C/I I/I I

0 CC I i@I CCI C) 2 0 400 600 8 1000 BIOMASS (g/rn~)

BIOMASS BY SPECIES 1.0 I

CII 4J O

I/I I/I ~

(D ~

I g 0.5 W

I CC I

CCI C) 500 1000 BIOMASS (g/m>)

Figure 4-8. Distribution of biomass in saw grass by component and species.

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LEAF BIOMASS 1'.0 Vl 5

m 4J O

Vl CA ~

~

cY m Cg 0

0 100 2 0 300 400 500 BIOMASS (g/m )

LEAF AREA 1.0 L

Cl 4k Vl a

EA ~

05 W

0 2.0 1.0 AREA (m>/m2)

Figure 4-9. Leaf biomass and leaf area in the saw grass zone.

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I TABLE 4-4 TOTAL BIOMASS OF SAW GRASS ON THE SOUTH DADE AREA (DRY WEIGHT AT 70'C)

Com onent g/m~

Live sawgrass 217.2 Dead sawgrass 317.8 Total 635.0 a

Dry weight at 70'C.

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TABLE 4-:5 DISTRIBUTION OF BIOMASS (9/m ) IN THE VARIOUS VEGETATIVE ZONES ON THE SOUTH DADE AREA EXCLUSIVE OF HAMMOCK BIOMASS Stations Ve etative zone 1-5 6-12 13-20 21-27 28-34 35-37 RED MANGROVES Fruit 0.6 1.0 0.9 Leaves 0.6 0.6 0.3 68.0 116.6 99.3 Branches 1.6 1.6 0. 8 168.0 288.0 245.4 Wood 2.1 2.1 1.1 227.7 390.3 332.6 Prop roots 3.6 3.6 1.5 319.7 548.1 467.0 Subtotal 7.9 7.9 3.7 784.0 1344.0 1145.2 BLACK MANGROVES Leaves 3.8 0.6 1.3 8.9 Branches 7.5 1 ~ 2 2.5 17.4 Wood 1.8 0.3 0.6 4.3 Subtotal 13. 1 2.1 4.4 30.6 WHITE MANGROVES Leaves 2. 5 34.1 9.2 3.2 Branches 4.3 58.2 15.6 5.5 Wood 13.1 176.1 47.2 16.6 Subtotal 19.9 268.4 72.0 25.3 BI ACK RUSH 1.0 1.0 Live Dead 72.0 112.0 89.0 148.0 0.0 '.0 Subtotal 184.0 237.0 1.0 1.0 SAW GRASS Live 217. 0 Dead 317.8 Subtotal 534.8 SALT GRASS 17.9 19.0 12.0 2.0 Total 591.0 481.0 329.1 842.9 1344.0 1145.2 4-20

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4.3 EFFECTS OF SOIL CHARACTERISTICS ON PLANT ASSOCIATION GROUPS

4. 3.1 Introduction The ability of soils in the South Dade study area to retain both litterfall and the resultant microbial products of decomposi-tion is a major factor in the maintenance and ultimate success of plant association groups. The habitat, however, is not a "closed system," where litter accumulation remains on a forest floor and nutrients are recycled within the community. The tidal runoff and freshwater sheet flow are major mechanisms by which litter material and soluble nutrients are transported into other plant communities and the waters of Card Sound. Thus, soil characteristics play a minor role in nutrient cycling. The distribution and sources of water play a more significant part in determining the plant distri-bution at the South Dade study area.

4. 3. 2 South Dade Soils South Dade soils fall into two categories: organic .and inor-ganic. The majority of the plant communities are found on inorganic calcitic substrates (previously described in Section 2.3:Soil Analy-ses and Characteristics). Calcitic soils are infertile due to the dominance of calcium and magnesium carbonates and only minimal amounts of other requisite elements. Calcitic-muds are products of the precipitation which occurs when calcium carbonate-saturated water interfaces with seawater.

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Organic soil components in the South Dade study area are associated with peats, which occur both in surface lenses forming the base of saltwater and freshwater hammocks, and in isolated pockets within the calcitic mud substrate. Further discussion of peats is included in Section 2.3.1:Major Soil Types.

4.3.3 Distribution of Hammocks The subsurface stratigraphy beneath the mangrove biome shows a shallow surface burden of loose calcareous mud and imbedded masses of red mangrove peat overlaying a limestone rock surface. Peat deposits were previously thought to be related to the distribution of the mangrove hammocks scattered throughout the study area, and the height of the trees was believed to correlate roughly with the depth and thickness of the deposit.

'I The distribution of subsurface peat deposits (see Figure 2-12 in Section 2.3.4) may be independent of the distribution of hammocks.

Peat deposits are sometimes found to be discontinuous and do not arise as a body from the limestone bedrock upward to the surface.

The presence of surface peat deposits does, of course, correlate with the presence of hammocks.

'Beneath the dwarf mangrove forests, peat deposits are also present but are not .contiguous with the surface. The calcareous marl of the dwarf forest zone contains a scattered mixture of roots and 4-22

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fiber remnants which are distributed uniformly throughout the marl soil. Therefore there is no evidence to suggest that autochthonous (deposited at place of origin) peat is being deposited in signifi-cant amounts in the dwarf mangrove zone.

4.3.4 Distribution of Man roves With the exception of hammock habitats, mangrove distribution (Section 2.2:Natural Plant Associations) at the South Dade study area was not found to be dependent upon specific soil types, but rather on the relative position of the community to the shoreline of Card Sound. tlangroves are considered to be open systems, that is, they are coupled hydraulically to both upstream and downstream systems.

Hater is the vehicle for the exchange of nutrients and chemical elements. Within the mangrove forest itself, water movements bring oxygen to the root system; remove carbon dioxide, toxic wastes, and organic debris; and continually maintain soil salt balance. The absence of flushing may result in an anaerobic (without oxygen) or reducing environment, which can build up toxic wastes and salt that may stunt or eliminate mangrove species.

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I 4.4 NUTRIENT TURNOVER IN SALT MARSHES 4.4.1 Introduction This section discusses the many studies conducted at the South Dade Area to determine how nutrients are recycled in salt marshes. Hydraulic studies demonstrated the importance of tides in moving nutrients out of and into the mangrove and grass zones, and nutrient determinations were made for all vegetation zones at multiple soil depths. These factors were studied to de-termine the contribution of mangroves to adjacent estuaries.

4.4.2 K draulic Studies The primary objective of the hydraulic studies was to de-scribe the movement of surface water along the study transect of the South Dade Area under various hydraulic and meteorolo-gical conditions. To achieve this objective, the principal factors that affect water motion in the study area were defined.

Methods r

Each of six stations (2, 9, 16, 21, 30, and 37) contained an instrument package that included a Stevens Type A Model 71 water-level recorder and a Hydrolab assembly used for gathering water-quality data. In addition to these six stations, a bay station (see Figure 4-10) was located about 25 meters east of 4-24

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'gtfre 4<<10 pproximate 1ocations of fresh and salt water interface-, August,I

. 1974. Station numbers -and bay station indicate position of instrument packages.

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Station 37, in Card Sound, and equipped with a Stevens water-level recorder. The water-level recorders were used to monitor the tidal cycle and seasonal changes in surface-water levels along the transect.

A dye study was performed to permit the calculation of water velocity as it moved inland from Card Sound. Rhodamine WT dye in plastic bags was dropped at Stations 30, 32, 34, and 37 from a heli-copter. The bags burst upon impact with the water. Photographs were taken about 30, 90 and 150 minutes following the dye drops.

Because the dye was moving along the transect, which was marked at 100-meter intervals, it was a relatively direct procedure to deter-mine the distance the dye patch moved from the point of origin.

Results Mean tidal elevations vary between months of the same year because of variations in relative positions of the sun and moon.

In general, the mean monthly tidal elevations were highest during the months of September, October and November. These months coin-cide with the south Florida wet season; however, the observed rise in tidal elevation was not attributable to temporary rainfall and runoff'ccumulation.

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The horizontal distance traveled by the landward edge of the water between high and low tides was generally about 300 meters.

During the period of September through November, however, water covered nearly the entire transect during average or higher than average tides, and little horizontal movement of the landward edge of water occurred. September through November was also the time when freshwater from rainfall runoff covered the upper portion of the transect and formed a continuous sheet of water with Card Sound water. Thus the majority of the study area is hydraulically linked with bay waters for about 25% of the year.

Between the saltwater and freshwater, a transition zone exists where mixing of the two types of water occurs. This transition zone was identified by sudden increases in electrical conductivity values. Seawater samples had a conductivity of about 54,000 pmhos/cmz, and the fresher water from upland runoff demonstrated conductivities of between 15,000 to 30,000 pmhos/cmz. The inland extent of salt-water was limited to Station 37 during August (See Figure 4-10).

However, as tide levels increased in subsequent months, the edge of saltwater extended as far inland as Stati'on 21.

The impact of water transport was observed at Stations 2 and 9, well'nto the saw grass zone. During the wet season, freshwater covers much of the transect and stands continuous with Card Sound water. As a result of hydraulic continuity, tidal variations 4-27

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were observed at these inland stations. Flow velocities near Stations 2 and 9 were low because the tidal amplitude was small and the ground slope was very shallow (about 0.004,: ).

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4.4.3 Nutrient Determination in Man rove Soils Nutrient determinations were made in all vegetation zones at multiple soil depths.

Methods for collecting soil samples have been described in Section 2.3.2 Soil Characteristics. Standard methods were used as described in APHA, 1971.

~Nitro en Total Kjeldahl nitrogen was determined for a series of soil samples from the study transect. Results of these analyses are given in Table 4-6. Subsoil samples were generally slightly richer in nitrogen than the overlying surface soils. Although some of the soils were typed as marls, some contained plant fibers. Peat soils were arbitrarily assumed to be those soils containing greater than 101 organic carbon and marl soils, less than 10Ã organic carbon.

The fibrous marls showed relatively higher nitrogen percentages.

All of the samples with high nitrogen percentages were either in or close to a hammock, with the exception of the hammock soils at Station 30. Although low values of nitrogen were found in this hammock, the nitrogen content increased with organic matter.

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TABLE 4-6 TOTAL KJELDAHL NITROGEN IN SOUTH DADE SOILS DURING NOYEHBER Station De th T e /TKN 0-6" marl 0.38 6-12" marl 0.49 0-6" peat 2.82 6-12" peat 2.16 12-18" mal 1 0.41 0-6" peat 1.94 6-12" marl 2.20 0-6" peat 0.50 6-12" marl 0.40 12-18" marl 0.46 0-6" marl 0.56 6-12" marl 0.40 0-6" peat 2.29 6-12" peat 2.33 15 0-6" marl 0.69 15 6-12" marl 2.12 16 0-6" marl 0.40 16 6-12" marl 0.58 17 6-12" marl 0.41 22 0-6" marl 0.37

'22 6-12" peat 0.96 23 6-12" marl 0.66 24 0-6" marl 0.4?

24 6-12" peat 0.75 30 0-6" marl 1.10 30 6-12" marl 1.73 30 0-6" hammock 0.44 30 6-12" hammock 0.17 4-30

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Phos horus Inorganic phosphorus determinations were made on the surface soils of the South Dade Area transect. In all cases the inor-ganic phosphorus concentration was somewhat lower in February than in November. This difference indicated a cyclical pattern in the amount of inorganic phosphorus in the soil. Tables 4-7 and 4-8 show that throughout the year the major forms of phosphorus were the easily extractable and calcium-bound phosphates. These two fractions were predominant in both the topsoil and the subsoil in the same order of magnitude of concentration. The topsoil, however, showed a greater amount of each form of phosphate than the subsoil.

Peat samples, especially those from depths of over 30.5 cm, were especially poor in extractable phosphorus, but calcium phosphate was present in "normal" concentrations. The analysis of extractable*

phosphorus in the surface soils at Station 3 showed a very high value, 'which is believed to be inaccurate.

Very few aluminum and iron phosphates were found in the area.

This was not unexpected as no clay minerals were present and the pH of the soi 1 solution was such that the formation of calcium phosphate and extractable phosphorus is favored over that of aluminum and iron phosphates. The range of total inorganic phosphorus along the transect showed no outstanding trends. Calcium phosphate seemed to a

decrease in concentrations toward the Sound.

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TABLE 4-7 INORGANIC PHOSPHORUS ANALYSES OF SOUTH DADE SOILS DURING THE MINTER (NOVEMBER) 01 xtracta e Ca- '-P 'e-P Total

'/~6" Station De th t e -P(x10-~) xl0 ~) (xl0-~) (xl0-~) Inor -P I 0-6" marl Oa 0. 380 0 0 0.00380 2. 745 6-12" marl 0 0.245 0 n/db 0.00245 1. 770 4.515 0-6" marl 0. 315 0.655 n/d n/d 0.00970 7.007 6-12" marl 0.065 0.330 n/d n/d 0.00395 2.853 12-18" marl .

0.010 0.360 n/d n/d 0.00370 2.673 12.532 0-6" marl 9.200 0.695 n/d n/d 0.09895 71.479 6-12" mar 1 0.405 0.345 n/d n/d 0.00750 5.417 76.897 0-6" marl 0.015 0.400 0 0.045 0.00460 3.344 6-12" peat 0.015 0.265 0 n/d 0.00280 3.231 12-18" peat 0.010 0.275 0 n/d 0.00285 1. 151 7.726 0-6" marl 0.045 0.043 0 n/d 0.00475 3. 453 6-12" marl 0.020 . 0.285 0 n/d 0.00305 2. 217 5.670 0-6" marl 0.180 0.490 n/d n/d 0.00670 4. 817 6-12" peat 0.015 0.350 n/d n/d 0.00365 2.653 7.524 15 0-6" marl 0.050 0.590 0 n/d 0.00640 5.197 6-12" marl 0 '60 0.495 n/d n/d 0.00550 4.451 9,630 0-6" marl 0.035 0.360 0 0 0.00395 3.197 6-12" marl 0.010 0.240 0 0.040 0.00295 2.387 5.584 17 0-6" marl 0.045 0.330 0 0 0.00375 3.035 6-12" marl 0.010 0.290 0 0 0.00300 2.428 5. 463 a Indicates concentrations below detection limits.

>>ndicates interfering color or other matter which prevented analysis.

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TABLE 4-7 (continued)

INORGANIC PHOSPHORUS ANALYSES OF SOUTH DADE SOILS DURING THE WINTER (NOVEMBER)

Soil X Extractable X Ca-P XA1-P XFe-P X Total Station. De th t e -P xl0 ~ xl0 ~ xl0 ~ x10 Inpr -P P/m .6" P/m~

22 0-6" marl 0.025 0.375 0 0 0 '0400 3. 523 6-12" marl 0.020 0.330 0 n/d 0.00350 3.083 6.606 23 0-6" marl 0.600 0.420 0 0 0.01020 8.985 6-12" marl 0.020 0.285 0 0.035 0.00340 2.995 11.980 24 0-6" marl 0.020 0.440 0 0 0.00460 4.052 6-12" marl 0.015 0.285 0 n/d 0.00300 2.643 6.695 30 0-6" marl 0.045 0.300 0 0 0.00345 2.634 6-12" marl 0 0. 215 0 =

0 0.00215 1.642 4.276 0-6" hammock 0.070 0.435 0.120 n/d 0.00625 3.781 6-12" hammock 0.020 0.315 0.085 n/d 0.00420 2.541 6.322

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TABLE 4-8 INORGANIC PHOSPHORUS ANALYSES OF SOUTH DADE SOILS DURING SPRING (FEBRUARY)

Soil 5 Extractable X Ca-P 'AA1-P XFe-P Total Station De th t e -P x10-~ x10-~) xl0-z xl0-~) Inor -P P m~.6" P m~

0-6" marl 0 110

~ 0.515 0. 020'a n/db 0.00645 4.659 6-12" marl 0. 015 0.065 n/d 0.00080 0.578 5.237 0-6" marl 0.105 0.515 0.040 n/d 0.00660 4 '98 6-12" marl 0.025 0.030 0 n/d 0.00055 0.400 5.198 0-6" marl 0.045 0.125 0 n/d 0.00175 1.272 6-12" marl 0.010 0.055 0 n/d 0.00065 0 '73 1.745 0-6" marl 0.165 0.445 0 n/d 0.00610 4.434 6-12" peat 0.015 0.195 0 n/d 0.00210 0.848 5.282 15 0-6" marl 0.090 0.275 0 n/d 0.00365 2.954 6-12" marl 0.035 0.195 0 n/d 0.00230 1.861 12-18" marl 0 0.011 0 n/d 0.00011 0.089 4. 904 16 0-6" marl 0.035 0.125 0 0 0.00160 1.295 6-12" marl 0.020 0.250 0 n/d 0.00270 2.185 12-18" marl 0.010 0.060 0 n/d 0.00070 0.566 4.046 17 0-6" marl 0.020 0.105 0 0 0.00125 1.011 21 0-6" marl 0.025 0.085 0 0 0.001]0 0.969 6-12," marl 0.025 0.120 0 0 0.00145 1.277 12-18" marl 0 0.030 0 0 0.00300 0.264 1. 385 22 0-6" marl 0.040 0.125 0 0 0.00165 1.453 6-12" marl 0.065 0.175 0 n/d 0.00405 3.568 12-18" peat 0 ..015 0.130 0 n/d 0.00145 0.853 5.856 23 0-6" marl 0. 035 0.195 0 0 0.00230 2.026 6-12" mar 1 0.045 0.160 0 n/d 0.00205 1.806 12'18" eat 0.010 0.125 0 n/d 0.00135 0.778 4. 610 aIndicates concentrations below detection limits.

bIndicates interfering color or other matter which prevented analysis.

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TABLE 4-8 (continued)

INORGANIC PHOSPHORUS ANALYSES OF SOUTH DADE SOILS DURING SPRING (FEBRUARY)

Soil 5 Extractable X Ca-P XAl-P XFe-P X Total Station De th t e -P x10 xl0 xl0 xl0- Inor -P P/m~.6" P/m~

26 0-6" marl 0 0.050 0 0 0.00050 0.440 6-12" marl 0 0.050 0 0 0.00050 0.440 0.880 29 0-6" marl 0.070 0.240 0 n/d 0.00310 2.367 6-12" peat 0.030 0. 185 0.015 n/d 0.00230 l. 392 3. 759

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Total phosphorus values demonstrated no discernable trend along the transect. However, the percentage of total phosphorus generally decreased with increasing soil depth.

Most of the soil phosphorus was in the form of organic phosphorus., The percentage of organic phosphorus ranged from a low of 18.35! at Station 8 to a high of 93.254 at Station 15, and the average percentage ranged from 70 to 85% of the total. Table 4-9 lists the results of the total phosphorus determinations for the South Dade study area soils.

Substantially higher values of phosphorus were obtained in samples that contained large amounts of organic matter, but the general phosphorus content was quite low compared with the soils of other mangrove areas. These low phosphorus levels could indicate that phosphorus is a limiting nutrient in the South Dade system.

Micronutrients Many of the micronutrient elements in the soils were quan-tified by carbonate fusion analysis. Magnesium and potassium increased with increasing organic matter, while manganese, strontium and zinc decreased with increasing matter. An example of these fluctuations can be seen at Station 7 (Table 4-10). Two samples were taken from the 15.25-30.50 cm level. One sample was marl (5.77Ã organic carbon) and the other was peat (27. 13/ organic carbon).

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II TABLE 4-9 INORGANIC, ORGANIC, TOTAL AND PERCENT OF TOTAL PHOSPHORUS VALUES OF SOUTH DADE SOILSa Soil n- rg- ot- rg- of Station t e (x10-~) (xl0 ~) (xl0 ) Total -P 6-12" marl 0.25 0. 21 0.46 46.27 0-6" marl 0,97 0.60, 0.70 85.98 6-12" marl 0.37 2.18 2.55 85.48 0-6" marl 0.65 0.98 1.62 60.21 6-12" marl 0.08 0.31 0.39 79.41 0-6" marl 0.46 1.39 1.85 75.12 6-12" peat 0.28 0.95 1.23 77.18 12-18" pea. 0.29 0.14 0.43 33.48 0-6" marl 0 '8 0. 20 0.68 0.37 29.88 18.35 6-12" marl 0.31 0.07 0-6" marl 0,67 2.58 3.25 79.37 6-12" peat 0,37 1.95 2.31 84.23 15 0-6" marl 0.37 1.53 1.89 80.70 6-12" marl 0.23 0.62 0 '5 72.98 12-18" marl 0.01 0.16 0.17 93.25 16 0-6" marl 0.16 0.62 0.78 79.45 6-12" marl 0.27 0.27 0.54 49.65 12-18" marl 0.07 0.39 0.46 84.69 17 0-6" marl 0.38 0.37 0.75 49,73 6-12" marl 0.30 0.07 0.37 18.70 21 0-6" marl 0.11 0.68 0.79 85.98 6-12" marl 0.15 0.21 0.35 58.64 0-6" marl 0.17 0.72 0.89 81.43 6-12" marl 0.41 1.50 1.90 78.69 12-18" peat 0.15 1.35 1.49 90.27 23 0-6" marl 0.23 0.57 0.80 71.36 6-12" marl 0.21 0.91 1,12 81, 66 12-18" peat 0.14 0.73 0.86 84.32 24 0-6" marl 0.46 0.76 1. 22 62.36 6-12" marl 0.30 0.58 0,88 65,91 29 0-6" marl 0.31 0.88 1,19 73.99 6-12" peat 0.23 0 '1 1.14 79.87 30 6-12" marl 0.22 0.22 0,44 50.91 0-6" hammock 0.63 1.6< 2.27 72,45 6-12" hammock 0.42 0.89 1.31 67,89 aAl1 values are in Percent air-dried soil.

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ll TABLE 4-10 MAGNESIUM, MANGANESE, POTASSIUM, STRONTIUM, AND ZINC ANALYSES OF THE SOUTH DADE SOILS Soil Station De th t e Mnxl0 Srxl 0 Znxl0 ~

6-12" marl 0.28 0.96 0.02 6.57 0. 70 0-6" peat 0.47 0.15 0.18 l. 27 0.23 6-12" peat 0.41 0.19 0.17 0.52 0.18 0-6" peat 0.46 0.81 0.12 5.04 6-12" marl 0.36 1.15 0.08 5.99 0. 76 0-6" peat 0.74 0.65 0.19 3.96 1.17 6-12" marl 0.41 0.95 0.06 5.62 6-12" peat 0.94 0.24 0.27 2.46 12-18" marl 0.46 0.84 0.08 6.43 1.19 0 6 peat 0.93 0.37 0.32 3.01 1.40 6-12" peat 1.03 0.17 0.42 0.74 0.45 15 0-6" marl 0.68 0.85 0.17 5.76 0 '2 6-12" marl 0.56 0.78 0.14 5.43 0.29 12-18" peat 0.74 0.66 0. 23 5.78 0.47 16 0 6ll marl 0.44 0.99 0.05 5.56 6-12" marl 0.44 0.95. 0.14 5.48 0.60 12-18" mal 1 0.54 0.86 0.10 6.01 0.72 17 0-6" marl 0.62 0.93 0.06 6.41 0.26 6-12" marl 0.48 0.85 0.11 5.92 2.07 21 0-6" mar 1 0.63 0.63 0.13 6.40 0.80 6-12" marl 0.75 0.93 0.18 6.33 0.53 22 0-6" marl 0.67 0.64 0.18 5.64 6-12" peat 1.13 0.07 0.56 0.87 0.47 12-18" peat 1.06 0.16 0.45 0.66 23 0-6" marl 0. 71 0.71 0.18 6.98 1. 23 6-12" marl 0.74 0.44 0.21 5.10 12-18" marl 0.01 0.26 0.28 3.01 2.04 24 0 marl 0.62 0.71 0.06 7.75 1.19 1 2<i peat 0.73 0.43 0.29 5.12 0.75 1.13 29 0-6" marl 76 0.37 0.22 7.53 6-12" peat 0.60 0.26 0 '3 4.35 0.57 0.72 30 6-12" marl 0. 53 0.57 0.24 6.,65 0-6" hammock 0.94 0. 34 0.34 4. 59 2.08 6-12" hammock 0.86 0. 30 0.31 4. 96 0.25 All values are in percent dry weight of soi l.

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Nitro en Fixation The results of the nitrogen fixation estimates for the sedi-ments are shown graphically in Figure 4-11 and for the algal mat in Figure 4-12. The highest sediment fixation rate estimated was 2.1xl0 sg nitrogen/g sediment/yr at Station 7, and the lowest was 3.3xl0 ~g nitrogen/g sediment/yr at Station 8, showing the extremely varied nature of the nitrogen-fixing abilities of the area. The blue-green algal mat showed a general decrease in nitrogen fixation from 6.5xl0 sg nitrogen/g mat/yr at the most landward station to 8.5x10 <g nitrogen/g mat/yr at the most seaward station.

The results of nitrogen fixation measurements on the 'South Dade Area compare favorably with the values found by other researchers (Brooks et al., 1969). It must be remembered that the estimates on the South Dade property reflect the minimum rate of nitrogen fixation to be expected over a yearly basis because minimum values are expected during winter months (Wilson, 1974) when the study was conducted. The minimum rates of nitrogen fixation are compar-able to average yearly rates from other estuarine areas, indicating a potentially significant nitrogen input (Fell, 1976).

One outstanding feature of the data is that they indicate a relationship between the presence or absence of water and rela-tive nitrogen fixing abilities. Stations 15-30 show a relatively similar rate of nitrogen fixation, in contrast with the more landward 4-39

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stations, which show higher rates and more erratic patterns of nitrogen fixation. This difference may indicate a relationship between nitrogen fixation rates and hydroperiod. Hardy et al. (1968) have shown that immersion in water decreases nitrogen fixation in legume nodules. Conversely, Hardy et al. (1971) have shown that the drying of the nodules also decreases nitrogen fixation abilities.

These studies contrast with the work of Paul et al. (1971), which showed increasing nitrogen fixation in soils with increasing moisture.

These studies could explain the trends in nitrogen fixation found on the South Dade property. Stations 15-30 were entirely inundated with standing waters and showed a marked reduction in nitrogen fixation rates. Station 1 also showed a low nitrogen fixation rate, which could be explained by the lack of water at the sample site. Stations 2-9, with the exception of Station 8, showed the highest fixation rates.

Stations 2-7 and 9 were subjected to alternate periods of wetting and exposure. The wetting and exposure to atmospheric nitrogen possi-

'I bly provided optimum conditions for nitrogen fixation. Station 8 was characterized by a slight depression between hammocks that held water and was entirely covered at the sampling time, so its low nitrogen fixation rate was not inconsistent.

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4.4.4 Or anic Carbon Productivit An assessment of ecosystem productivity is necessary in order to measure the response of an ecosystem to changes. A method to compare the productivity of different habitats is to measure the amount of organic carbon incorporated or "fixed" within the ecosystem.

As carbon is, the fundamental element in all biological materials, a change in the amount of carbon in the ecosystem is an indication of a redistribution or a change in the biomass of the system.

The productivity of a system is generally divided into organic matter produced by plants and organic matter produced by animals.

These two components are termed primary and secondary productivity, respectively. Primary productivity (plants) may be transferred to the secondary producers (animals) when the animals graze on growing plants or ingest litterfall materials. Because the secondary producers comprise but a minute fraction of the organic carbon fixed on the study site, the bulk of the study efforts was directed toward measure-ment of primary productivity.

Productivity, which is usually measured in terms of grams of carbon fixed per square meter per day, is divided into two categories:

net productivity and gross productivity. Gross productivity is the measure of all carbon material entering the system. Net productivity measures that amount which has been deducted from the gross produc-

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tivity for respiration and maintenance. Net productivity measures carbon available for incorporation into stems, leaves and roots.

Productivity of trees and rasses Methods - Metabolism and carbon fixation were measured by enclosing an area containing grasses and/or plants within a clear plastic chamber. When the plant was too large to be mon-itored within a chamber, a leafy. portion of a branch was enclosed in a plastic "balloon," which was held open by means of small.

air blowers. A Beckman tlodel 215B infrared gas analyzer mea-sured the COz that entered and left these chambers.

Results - Estimates for carbon fixation in grams of carbon per square meter of leaf surface on a yearly basis are provided for the following habitats: saw grass, black rush/

salt grass, hammock, dwarf mangrovesM.>d fringe forest mangrove.

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Once the productivity of each species in each vegetative zone of the South Dade property was estimated, the total production of the area was evaluated. The fringe forest production and respira-tion was assumed to be similar to that of the hammock red mangroves.

The leaf area of the black rush/salt grass zone was calculated as 1,65 square meter of leaf per square meter of habitat (mz/mz), or 8.27 grams of carbon per square decimeter per year (g C/dmz/yr) gross primary production by black rush/salt grass on a leaf area basis.

This is less than that of any of the mangrove species in either the dwarf mangrove zone or the saltwater hammocks.

Gas metabolism data were not obtained for the saw grass zone of the South Dade study area. Therefore, saw grass production was estimated from standing crop values reported i n Section 4.2, Vegetation Peak Stand-ing Crops, and were based upon the following assumptions:

1. Saw grass biomass turnover is at least 1005 every year; that is, at least as many blades of grass are produced as die each year (Snedaker, 1976).

2. Respiration and plant maintenance require about 50% of grass primary productivi ty (Snedaker, 1976).

The estimate for saw grass productivity is the lowest of any of the plant associations found on the South Dade study si te. It was calculated as follows:

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Net productivity = 411 g organic material/year 238 g C/m /yr 411 g organic material/year 238 g C/m~/yr Gross productivity = 822 g organic material/year 476 g C/m~/yr Productivit of Ph to lankton and Benthic Al ae Methods - In order to estimate the amount of carbon contributed by the phytoplanktonic and benthic algal communities, daily water quality records were assessed for changes in pH, dissolved oxygen, and temperature. Given the alkalinity and'change in pH of a water mass, the change in CO@ was calculated. The carbon production of the benthic algal community was measured during periods of standing water.

Results - Gross productivity for the benthic algal community was estimated to be 388.9 grams of carbon per square meter per year.

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4.4.5 Man rove Contribution to Adjacent Estuar The relative contribution of the South Dade Site to Card Sound waters was measured by experimentally determining the amount of detri-tal material exchanged between land and water. As tides flow across the flat plain during diurnal ebb and flood cycles, particles in the form of decomposed litter are swept along with the moving water. As detritus is rich in nutrients, the measurement of organic particulate matter demonstrates if the tidal habitat is losing, gaining, or maintaining its nutrients.

Methods The detrital export dynamics of the South Dade Site were eval-uated by both analytical and experimental methods. The analytical method utilized litterfall calculations based upon actual monthly litterfall measured in each vegetative zone. The experimental method involved direct monitoring of the detrital load during several tidal cycles over a representative area of the mangrove ecotone. The results of the experimental method, which were not performed for every month of the year, were then used to verify the results of the analytical method.

positionnThe determination of litterfall involves three parameters: the actual litter fall, the decomposition rate, and the actual amount of litter remaining on the surface. Given the litterfall and the decom-rate, a steady-state level of litter may be calculated by 4-47

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where: X ss

= the steady state amount, of litter L = actual 1 i tter fall rate K = the decomposition constant If the steady-state level of litter buildup is less than that calcu-lated, then the difference must be that exported by the tidal regime.

Conversely, if the actual litter amount is greater than that calcu-lated, then the difference is that amount of litter imported. Values for these parameters have been experimentally determined for each of the vegetative zones during this study.

Detrital export was determined experimentally by analyzing water samples, taken hourly over periods of co-equal tides. These periods of co-equal tides were determined from the U.S. Coast Guard Tide Tables for the Card Sound area in the vicinity of Pumpkin Key during the years 1973 and 1974. The periods monitored during this study were November 17-18, 1973 and January 25-26, 1974; and February 28-29 and October 29-30, 1976.

A sampling site for the November and January periods was selected approximately 0.5 km northeast of transect Station 37 which Co-equal tides are those having either the maximum or minimum levels at the same height in relation to a stationary datum. This insures the exchange of approximately equal amounts of water during the ebb and flood cycles of the study period.

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was characterized by being a slightly depressed area approximately 64 m wide. The sampling station was located approximately 15 m from the southwest "bank" of the sampling area. All water samples were withdrawn at a depth one-third the distance from the surface of the water to the bottom; For the 1976 sampling periods, a tidal creek located within the fringe mangrove at Station 37 was designated as the sampling site.

Water samples were pumped through a l-l/2" i.d. flexible rubber hose with a hand-operated diaphragm pump, Care was taken so that bottom materials were not disturbed during the sampling. The samples were pumped, into a plastic container through a ser ies of soil-testing sieves having mesh sizes of 2000pm (¹10), 600@m (¹30), 250pm (¹60),

125pm (¹120), and 62@m (¹230).

Based on information gained from the 1976 and 1974 sample periods, only the 250um and 62um sieves Were used to describe the particulate distribution since the amounts of particulate matter

>62pm was found to be rather small compared to suspended particles

<62pm.

The sieves were separated and the detrital material contained on each one was washed with water from the plastic container into small plastic bags, into which a solution of HgClz was added.

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A sample of the water in the plastic container was then placed in a glass jar and also fixed with HgClz.

The samples of detritus from each sieve were filtered with low suction through Matman 842 filter paper. The samples of water from the plastic container were filtered through 0.45am Mi llepore filter paper. Samples of the filtrate were then placed in small glass vials for dissolved organic analysis. That quantity of organic material in the 0.45pm size class is refer red to as "dissolved or-ganic matter."

The filter papers were placed in a drying oven at 70'C until a constant weight was obtained. The increased weight of the pre-weighed and dried filter paper was taken as the weight of detrital material. Small amounts (2 mg) of the dried detrital material in each size class were analyzed for carbon, ni trogen and hydrogen con-tent by a Perkin-Elmer Model 240 Elemental Analyser. ,The 'dissolved organic and total carbon content of the Millepore effluent was determined by a Beckman Model 915 Total Carbon Analyser.

The current velocity and water height were monitored during each of the sampling periods. The current velocity was measured by a Teledyne-Gurley Pygmy Current Heter, while the water height was measured in centimeters from the bottom by a conventional meter stick.

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The amount of water passing the sampling station was calculated using the geometry of the tidal aperture, the depth of the water and the current velocity. This quantity, with the measured amount of detritus in the water, was used to determine the total quantity of detritus imported or exported over the sampling period.

A watershed area was delineated by examining the water flow characteristics of the area as reflected by the vegetational orien-tations. This watershed area was used to calculate the detritus contribution of the upland areas on a mz basis .

Res ul ts Visual inspection of an enlargement of the aeri'al photograph of the South Dade Area revealed, on the basis of the vegetative orientation, that the predominant tidal water drainage was a simple linear process, described in Section 4.4.2, Hydraulic Studies.

The majority of the detrital export was in the form of small particulate matter between 0.45 and 62.04m in size. These particles were the major source of detrital export that entered the contiguous estuarine system of Card Sound.

The quantities of detrital material varied with the tides.

Table 4-11 gi ves the means and ranges of sizes of particulate organic matter obtained during late fall. Also, the dissolved 4-51

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TABLE 4-11 MEAN CONCENTRATIONS (mg/1) OF PARTICULATE DETRITAL MATERIAL IN THE TIDAL WATERS Particulate size ran e 0-Tidal sta e 2000pm 600qm 250pm 125wm 62pm 0.45pm Incoming tide Mean 0.077 0.049 0.112 0.058 0.082 46.881 Range 0. 009 0. 026 0.023 0.014 0.014 3.600

-0. 163 -0.085 -0.458 -0.116 -0.134 -106.829 Outgoing tide Mean 0.059 0.055 0.058 0.050 0.151 65.431 Range 0 011 0 005 0 015 0 013 0 038 11 555

-0.225 -0. 182 -0.224 -0. 107 -0. 728 -217. 111 4-52

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organic portion of the detritus constituted a higher percentage of the total detrital transport on the outgoing tide than on the in-coming tide. The reverse is true of the particulate matter. These data show that the detrital export is mostly in the form of small particulate matter.

The dissolved organic matter was analyzed in terms of carbon which was separated into three categories: total carbon, inorganic, and organic carbon. The results of these determinations are given in Table 4-12. The dissolved carbon values show that the outgoing waters were richer in organic carbon and poorer in inor'ganic carbon than the incoming waters.

The data obtained for the January sampling period showed a pattern similar to that for November, but 'lesser absolute amounts of dissolved organic matter were present in the water co'jumn.

The amounts of transported detrital organic material per meter of tidal aperture (Table 4-13) demonstrated a varying influx of detrital materials from coastal vegetation into Card Sound waters.

Upon comparison with November and January estimates, the actual quantities of import and export for February were low. Li tterfall rates usually decline in January and February, and litter is perhaps not as available for export in this month as it might be in December 4 ~r3

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TABLE 4-12 AMOUNTS OF TOTAL, INORGANIC, AND ORGANIC DISSOLVED CARBON (mg/1) IN THE TIDAL WATERS DURING NOVEMBER Tidal sta e Total C Inor anic C Or anic C Incoming tide 29. 4 15. 7 13. 7 Outgoing tide 27. 4 12. 8 14. 6 4-54

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TABLE 4-13 MEASURED TRANSPORT OF DETRITAL ORGANIC MATTER (KG DRY WEIGHT OF ORGANIC MATTER PER METER OF TIDAL APERTURE)

DURING JANUARY, FEBRUARY, OCTOBER AND NOVEMBER 1976 Januar Februar October November Mean Import per Hour 8.31 3.54 2.48 10.43 Mean Import per Tide 49.85 21.24 14.87 62.58 Mean Import per Day 99.70 42.48 29.75 125.16 Mean Export per Hour 8.89 1.74 2.86 11.26 Mean Export per Tide 53.89 10.44 17.16 67.56 Mean Export per Day 107.78 20.88 34.32 135.12 Total Net Export per Day 8. 08 -21. 60 4.57 9.96

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and January. In February more detrital organic'matter entered the habitat from the water column than was exported, probably due to reduced litterfall in January and February.

To relate the potential nutrient contribution of the detrital organic matter from the various habitats of the South Dade study area, the elemental composition of the litterfall was measured.

Litterfall was collected from dwarf mangrove, saltwater haranock, fringe forest, black rush/salt grass, and saw grass habitats. These were allowed to decompose for 70 days, and were analyzed for selected elements (Table 4-14 ).

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TABLE 4-14 ELEMENTAL COMPOSITION OF DETRITUS AFTER 70 DAYS OF DECOR'OSITION ercen ry welg pm ry weig Zone Sr Zn Dwarf mangrove 41. 6 0.46 0.014 0.463 0.768 163 55 22 Saltwater hammock 39. 2 0.47 0.013 0.675 0.825 64 16 Fringe Forest 33. 7 0.94 0.038 0. 310 0. 100 232 60 18 Black rush/

salt grass 54 1.2 0.022 0.285 0.079 31 53 39 Saw grass 52 0.9 0.016 0.230 0.070 25 70 16

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4.5 EFFECTS OF GROUNDWATER SEEPAGE ON MANGROVES The effects of increased groundwater seepage on mangrove communities can be inferred from the data produced from the South Dade studies. Different mangrove species respond in various ways when exposed to varying saline regimes. Likewise, exposure to in-creasingly fresh water was shown to have a profound effect on the distribution of mangrove species. This effect appears to be unre-lated to either freshwater or saltwater tolerance by mangroves.

4.5.1 Distribution of Vegetation Frequency of occurrence (Section 2.2) data indicate that highly saline environments support significantly fewer species than brackish or freshwater environments. The fringe forest, for example, is almost exclusively composed of red mangrove, but 19 different species were found in the saw grass habitat. There is a strong inverse relationship between the salinity of available water and the number of plant species existing in the habitat. Mangroves have no known metabolic need for high concentrations of salt. Their presence in high saline zones reflects the inability of other plant species to cope with the physiological stresses imposed by salt-induced osmotic pressures. Plants which live successfully in saline environments either physically reject salts which become i ncorporated in plant tissues, or they possess mechanisms which allow freshwater but deny saltwater access through the root cell membranes. Plants which are not adapted to saltwater habitats do not survive, and the ground and 4-58

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air space become available to those plant species that can tolerate the habitat. As the habitat becomes more severe, the contenders for that habitat become less numerous. Not always is habitat tolerance by plants expressed in absolute terms such as "presence" or "absence."

Gradations of tolerance for a habitat may be manifested within a single species. As physical strength and stamina vary tremendously within the human population, so hardy individuals of the plant community will extend into environments that test the maximum capability to survive. Obviously, those individuals living on the fringe of environmental acceptability will be few in number when compared with the whole population.

By applying the above concepts to the question of seepage in mangroves, one could reasonably expect the following: increased salt-water seepage at seawater concentrations (about 35%, ) would tend to favor growth of mangrove species at the expense of the less salt-tolerant vegetation. Conversely, seepage from freshwater sources would favor the invasion of freshwater species into regions dominated by mangroves.

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4.6

SUMMARY

During the dry season, the influence of normal tides generally did not extend beyond Station 28. The distance traveled by the land-ward edge of water between high and low tides was generally about 300 meters.

During the wet season, and especially September through Novem-ber, standing freshwater from rainfall was continuous with Card Sound water and covered the inland portions of the transect. Normal tidal motion was imparted to the freshwater, and tidal effects were there-fore observed along nearly the entire length of the transect.

When freshwater was continuous with Card Sound water, a transition zone existed between the freshwater and saltwater. During the data collection period, the position of the seaward edge of this transition zone fluctuated between Stations 21 and 30.

Rainfall had a significant effect on the volume of water flushed from the site. The water surface profile responded quickly to rainfall.

Once the productivity of each species in each vegetation zone was established, the total production of the area was calculated.

Table 4-15 summarizes the yearly production of the vegetative zones.

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These data show that the total productivity values for the entire South Dade property were:

Gross productivity = 1.2 x 10 '~ grams carbon/year Respiration = 8.2 x 10>o grams carbon/year Net productivity = 4.1 x 10>o grams carbon/year 4-61

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TABLE 4-15 SUMMARIES OF THE RESPIRATION AND PRODUCTION VALUES BY VEGETATIVE ZONE Vegetation Net Gross Zone roductivi t Respiration roductivity Fringe forest 513.2,g C/m /yr 4165.0 g C/mz/yr 4678.2 g C/mz/yr Dwarf mangrove 60.3 g C/m /yr 4362.0 g C/m /yr 4422.3 g C/m /yr Saltwater hammock 790.0 g C/m /yr 4505.0 g C/m /yr 5295.0 g C/m /yr Black rush 362.0 g C/mz/yr 1004.0 g C/m /yr 1366.0 g C/mz/yr Saw grass 238.0 g C/m /yr 238.0 g C/mz/yr 476.0 g C/m /yr Algae 5 benthos -6.4 g C/mz/yr 395. 3 g C/m /yr 388.9 g C/mz/yr The total area of the algal mat and benthos is assumed to be that of the scrub zone plus the fringe forest.

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LITERATURE CITED Abbott, R.T. 1974. American seashells, 2nd ed. Van Nostrand Rein-hold Co., New York. 663 pp.

ABI. 1976. Ecological'monitoring of'elected parameters at the Turkey Point Plant. Annual Report. AB-43. Prepared by Applied Biology, Inc., for Florida Power 8 Light Co., Miami, Florida.

ABI. 1977a. An evaluation of habitats associated with rare and endan-.

gered 'species at four sites in Dade County, Florida. AB-,36.

Prepared by Applied Biology, Inc., for 'Florida Power 8 light Co.,

Miami,, Florida.

ABI. 1977b. An evaluation "of agricultural potential of five sites in Dade County, Florida. AB-45. Prepared by Applied Biology, Inc.,

for Florida Power 8 Light Co., Miami,, Florida.

APHA. 1971. Standard methods for the examination of water and waste water., 13th ed. Amer ican Public Health Association, Washington, D.C. 874 pp.

Bailey, R.M., J.E. Fitch, E.S. Herald; E.A. Lachner, C.C. Lindsey, C.R. Robins, and W.B. Scott. 1970. A list of common and

'cientific names of fishes from the United States and Canada, 3rd ed. "Amer. Fish. Soc. Spec. Publ. No. 6. 149 pp.

r Barlow, T.P. '955. Physical and biological processes determining the distribution of zooplankton in a tidal estuary. Biol.

Bul. Mar. Biol. Lab., Woods Hole, 109:211-'225.

Brooks, R., P.L. Br ezonik, H.D. Putnam, and M.A. Kerra. 1969. Nitrogen fixation in an estuarine environment: the Waccasassa on the Florida Gulf Coast. Limn. and Oceanog. 16:701-710.

Bull, J. and J. Farrand, Jr. 1977. The Audubon Society field quide to North American birds - eastern region. Alfred A, Knopf, New York. 775 pp.

Conant, R. 1975. Field guide to reptiles and amphibians of Eastern and Central North America. Houghton Mifflin,Co., Boston. 429 pp.

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LITERATURE CITED (continued)

Craighead, F.C., Sr. 1971. The trees of South Florida, Volume I:

the natural environments and their succession. Univ. of Miami Press, Coral Gables, Fla. 212 pp.

Dames 8 Moore. 1976. Surface water investigation; South Dade biological study, South Dade area. Prepared for Florida Power & Light Co.,

Miami, Florida Fell, J.W. et al., 1976. The role of microorganisms as indicators of changi ng environmental condi tions in mangrove and marsh communi-ties. A final report (Section A) on a research project in South Dade County submitted to Florida Power 5 Light Co., Miami, Florida.

Fincher, E.L. 1976. Ecological studies of a subtropical terrestrial biome: microbial ecology. Suraaary report, March 1, 1976-August 31, 1976. Project No. G32-630. Prepared for Florida Power 5 Light Co., Miami, Florida.

Hardy, R.W.F., R,C. Burns, and R.D. Holsten. 1971. Applications of the acetylene-ethylene assay for measuring of nitrogen fixation.

Symposium Nitr. Econ. of Plant Commun., 12th Pac. Sci. Conf.,

Canberra, Australia.

Hardy, R.W.F., R.D. Holsten, E.K. Jackson, and R.C. Burns. 1968.

The acetylene-ethylene assay for Nz fixation: laboratory and field evaluation. Plant Physiology 43:1185-1207.

Paul, E.A., W.A. Rice, and R.J. Myers. 1971. Nitrogen fixation in grassland and associated cultivated ecosystems. rn. T.A. Lie and E.G. Mulder, eds. Biological nitrogen fixation in natural and agricultural habitats.

Snedaker, S.C. 1976. Ecological studies on a subtropical terrestrial biome. Final report. Prepared for Florida Power 5 Light Co.,

Miami, Florida.

Wi lson, S.U. 1974. Metabolism and biology of a blue-green algal mat. M.S. Thesis, Univ. of Miami.

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