HISTORIC CREEK WATERSHED STUDY FINAL RESULTS: YEAR 1

By

John F. Meeder Peter W. Harlem

Amy Renshaw

Southeast Environmental Research Center Florida International University Miami, FL 33199

To Richard Alleman South Florida Water Management District West Palm Beach, FL 33406

18 Oct 20011 EXECUTIVE SUMMARY

The major goals of this study were to: 1) identify a tidal creek site for restoration of freshwater discharge, 2) determine the predevelopment near shore salinity regime, and 3) determine the discharge of freshwater required to produce the target salinity. This was done in several stages. The first stage was to identify all the historic tidal creeks along western Biscayne Bay from the Deering Estate southward to Convoy Point. This was completed using aerial imagery and ground truthing. This survey resulted in the location of 48 tidal creeks of which, only several were deemed likely choices because of pollution,ownership, degree of restoration required, and access problems. The area between the L31E canal and Biscayne Bay from Military Canal to point 800M north of the Military Canal was selected. This site had a well-developed tidal creek that merged westward into a freshwater slough and transverse glades. In addition, oyster shell deposits were located in several areas within this basin indicating that historic conditions were estuarine in nature. The second stage was to produce a topographic-bathymetric map of the study area for the present, as well as, historic conditions at the turn of the century. This was done to determine if restoration success would be likely. The distribution of oyster deposits, old channels, and flow ways helped to provide a guide for restoration. Creek cross-section changed greatly from the Bay toward the levee where tidal action did not maintain the channel. The third stage was to determine a target salinity regime for the estuarine zone. Using the oyster, Crassostrea virginica ’s ecological requirements as the major paleoecological tool, a target salinity regime of 5 to 15 parts per thousand (ppt) for the wet season and 10 to 19 ppt for the dry season was established. The final stage was to calculate the volume of freshwater needed to produce the desired salinity regime. A first approximation of freshwater delivery required is 10 ac-ft/d during the dry season and 15 ac-ft/d during the wet season. The calculation of required freshwater discharge used a simple formula balancing water loss against water gain processes. Water loss processes included evaporation from water bodies, evapotranspiration from marsh surface, tidal egress volume (calculated for spring tide only), discharge into bay and bay water renewal time. Water renewal time was very difficult to calculate and was estimated by calculating tidal volume, bay volume, basin bathymetry, and prevailing wind directions. The error associated with this calculation was the main reason a post discharge salinity monitoring program is recommended in order to adjust discharge according to actual field salinity measurements. We are confident that the figure presented is a reasonable estimated based upon methodology and funding level. Water gain processes include tidal ingress (calculated only for spring tides), canal discharge and rainfall.2 INTRODUCTION

Biscayne Bay has undergone numerous anthropogenic changes, most during the period 1880 to 1980. Changes include the physical regime (Michel, 1976), freshwater discharge (Buchanan and Klein, 1976), chemical regime (Waite, 1976), sedimentary environments and processes (Wanless, 1976; Harlem, 1979), and biological regime (Thorhaug et al ., 1976). The most profound changes in the Bay are found in the North Bay region where most of the bottom, shorelines, and water circulation are highly altered (Harlem, 1979). North Bay was brackish in nature because of considerable freshwater discharge from the Everglades and poor circulation to the Atlantic Ocean prior to the construction of Haulover Cut. North Bay contained many oyster bars, which supported a small industry at the turn of the century (Smith, 1895; Handbury, 1896; Munroe and Gilpin, 1930). This industry was lost as a result of increasing salinity associated with the inlet cut construction, drainage of the Everglades, and the construction of the Intracoastal Waterway. Other evidence of the estuarine nature of the northern Bay is the fish catch records, which showed more species and more frequent catches of estuarine dependant species in and around the Bay (Serafy, 1997) in the past. Lost oyster fisheries associated with increased salinities is a familiar situation in other areas of Florida such as the Ten Thousand Islands (Tebeau, 1966; Tebeau, 1991).

The estuarine nature of the southwestern coastline and near shore areas of South Bay is not as well documented. However, the earliest aerial photographs and descriptions document that freshwater marshes continued almost to the edge of the Bay and that transverse glades cut across the limestone ridge and spread out into broad sloughs to the Bay through numerous creeks. These creeks were tidally influenced within a 100M or so of the shoreline ( Figure 1 ). Freshwater marl soils are presently exposed submerged in the near shore area documenting sea level rise, saltwater encroachment, and coastline retreat. This condition is found throughout South Florida (Meeder et al ., 1999). Sheet flow and groundwater discharge both have decreased with Everglades drainage and have been replaced by canal discharge, which does not have natural timing and is a point source to the Bay. Parker (1955, 1974) documents that the water table throughout Miami-Dade County has dropped between 4 to 6 feet since the turn of the century. In addition, oysters were quite common along the western shore of Biscayne Bay, where creeks dumped freshwater. The construction of the L-31E protection levee and canal complex completely eliminated sheet flow to the Bay in the mid 1960’s.

The purpose of this study was to identify a creek system that might be restorable to predevelopment conditions in terms of coastal salinity regime. In other words, to reestablish an estuarine zone in the near shore area by discharging water into an historic creek system that we know supported oysters in the past. The two major tasks were to: 1) establish a proper salinity regime to target and to 2) develop a model to estimate the volume of freshwater needed to achieve the target salinity regime.3 SITE SELECTION

The area from Military Canal northwards to Fender Point was selected as a study site after a characterization of historic Biscayne Bay watersheds was completed (Meeder et al ., 1999), and a review meeting held with the South Florida Water Management District project manager and National Park Service personnel( Figure 1 ).

Figure 1

. A 1940 aerial photograph illustrating the study area watershed. Note that the southern branch of the transverse glades slough (large arrow in NW corner of photo) spreads out and develops into 4 distinct tidal creek systems. Creek No. 2 was selected as the study area. Note: Tidal influence is defined by the distribution of red mangroves (appear as dark bands along the coastline and along tidal creek banks and levees).4 SITE CHARACTERIZATION

Ecosystem model: General site description. The purpose of the schematic ecosystem model is to describe the relationships between ecosystem components and estuarine salinity and oyster ecology ( Figure 2 ). The two boxes represent the coastal wetland and the near shore estuarine ecosystems. Ecosystem components or forces not originating within an ecosystem are identified in circles outside and to the top of the two ecosystem boxes. The interrelationships between external components (or processes) and components of the two ecosystems, as well as, between ecosystems are denoted by arrows. This flow chart is basically what we used to determine both the target salinity and freshwater discharge required to maintain the target salinity regime. All the components that drive the hydrology and salinity are approximated and discussed in detail in later sections.

The coastal wetland system can be described as a red mangrove tall scrub forest,which occupies a topographic basin bound on the north and south by west-to-east infilled tidal creeks and creek levees and the coastal levee to the east. The creek levee and coastal levee are covered by taller more diverse forest of red and black mangroves along the creeks and coastline with tall white mangroves also found landward of the coastal levee. Creek No. 2 ( Figure 1 ) was a large tidal creek whose headwaters gradually developed into a freshwater slough. This tidal creek was fed historically by freshwaterdischarge from the Everglades and now has potential to receive freshwater from the L31E canal. Wetland water is a mixture of canal discharge, rainfall minus evapotranspiration (ET) and Biscayne Bay tidal water with episodic additions from tropical depression storm surges. The proportion of wetland water sources change seasonally, resulting in seasonal salinity changes related to freshwater discharge, bay water salinity, rainfall surplus, and tidal height and exchange rate. Salinity controls the plant species composition and subsequently soil accretion rate. Freshwater discharge, tide height and storm surge height control suspended sediment concentrations and import/export.

The estuarine ecosystem has direct exchange with the coastal wetland ecosystem through links between hydrology. The interrelationships among hydrologic components determine salinity and suspended sediment’s ultimate fate. Tides (tidal water at this location is a mixture of Biscayne Bay seawater and Mowry Canal (C-103) discharge), groundwater discharge, rainfall surplus, and water renewal times interact to produce the near shore water and salinity regimes. Estuarine salinity and sufficient water currents to maintain sediments in suspension are required for oyster development. Water and suspended sediments are almost freely exchanged with Biscayne Bay, which is controlled, by bathymetry, wind strength and direction, freshwater discharge, and tide height. The proposed estuarine zone bottom types range from outcropping bedrock in the southern area to an organic rich marine sandy mud with considerable skeletal material, mostly mollusk fragments. This marine sediment generally thickens towards the north and west. Exposed freshwater marl and mangrove peat is common along the shoreline.5 The model also was used to address the two major concerns in the feasibility of rehydration of the tidal creek system and development of the estuarine zone which are: 1) has the marsh topography changed from deposition and erosion processes so much that effective freshwater delivery will not be able to be achieved, and 2) has the coastal basin’s characteristics been altered so that reestablishment of the estuarine zone is unlikely? The several ecosystem components or rates at which they work may be affected by changes in topography and water delivery patterns, both spatially and temporal. Examples include: freshwater retention time in the wetland and estuary can be increased or decreased by changes in basin volume and channel flow through the wetland and into the estuarine basin can be highly altered or lost entirely. These questions are further discussed later in this section.

Figure 2

. The schematic ecosystem model. The two boxes represent the two ecosystems; coastal wetlands and near shore Biscayne Bay. The circles above or outside the ecosystem6 boxes are components that affect the two ecosystems from outside the systems by management of natural forces such as rainfall. The components inside the ecosystem boxes represent the major components of each respective system and the arrows describe the relationships between each ecosystem component.

Aerial photography.The first step to answering the above two questions was to look at serial aerial photography of the study area in order to establish visual changes ( Figure 3 ). Aerials from 1928, 1940, 1992 and 1998 were used intensively and other imagery from the 1960-70’s was consulted. Several changes are very noticeable: 1) the width of the mangroves along the coast and along the tidal creek increase with time, 2) the entire marl prairie habitat (light in color) was replaced my mangroves (prior to the early 1970’s), 3) the embayment north and northwest of the island silted in and was covered by mangroves, and 4) about 30M of coastline erosion has occurred. The magnitude of observed changes in the system required more detailed studies of both present and past conditions.

Figure 3

. Aerial photography used for historic change analyzed. Scale is the same for the four photos. The L-31E structure was not present in 1928 and 1940. Note: the island south of the point shows an origin further offshore than the area it presently occupies.7 Present topography/bathymetry.The second step was to define present topography/bathymetry using standard surveying methods to produce a topography map of the coastal wetlands with a 25mm elevation contour. Standing water levels were also used to supplement survey lines. The bathymetry map contour interval was 30cm (Figure 4 ). Contour patterns were produced by wading transects at high tide. The locations of the survey and depth control lines are also presented.

Figure 4

. Topography of wetlands in 2.5cm elevation contours. Survey was made using a level with accuracy of 1cm/100M. We closed each shot and only made shots less than 50M. If closure was off by more than 1cm, we reshot the elevation. Water levels in the marsh at high slack tides were also used to supplement survey lines. Bathymetry depth contour intervals are 30cm and were produced by wading transects at high tide.

Topography defined one major tidal creek (No. 2, Figure 1 ). It was a topographic high from the levee eastward approximately 200M where it attained a channel morphology with well-developed channel levees which disappeared approximately 150M from the coast (Meeder et al ., 2000). At the point where the natural creek levees were reduced the creek channel tended to break up into ill-defined channels. A poorly defined slough crossed west to east approximately 150M south of the main channel and connected several small tree islands. The last tidal creek was approximately 300M south of the main creek and is highly disrupted by a drainage canal. This canal should be backfilled or it may pirate freshwater and delivery straight to the Bay to the southernmost8 part of the proposed estuarine zone. Between the two large creeks from the levee to a distance eastward of 450M was a topographic basin of nearly 10cm in relief. The area, approximately 100M wide between 450 and 425mm in elevation, was a near continuous band north-to-south and forms the eastern rim of the interior basin. The marsh east of 550M from the levee had irregular topography as the marsh was dissected by numerous small distributaries and marsh loss (perhaps post Hurricane Andrew subsidence) to the eroding shoreline. Along the shoreline, a coastal levee was the highest feature near the coast, but in this area was discontinuous.

The proposed estuarine zone had a maximum depth of 20cm at high tide. The maximum depth was located south of the island and was an earlier Holocene creek channel. Offshore of the fringing mangroves along most of the coastline was a thin marine mud or inundated red mangrove peat, which was exposed during most wet season low tides and most of the dry season. This narrow zone frequently had very little aquatic vegetation cover. The bottom deepened at a rather constant rate from the shoreline to the depth of approximately 125cm, where the water depth increased at a faster rate. Between the channel and the island approximately 45cm of sediment covered the bedrock, forming a shoaling wedge shaped sediment body. The island was approximately 120M in length and 40M in width and is aligned in a southeast-northwest direction. The island was made up of oyster rich skeletal material. At high tide the island was almost totally inundated and red mangrove trees cover most of the island. This island was first believed to be a dredged canal spoil bank. However, no channels were located anywhere near it, and the coastal canal almost directly to the west did not exhibit oyster shells along the banks or in adjacent soils. Furthermore, skeletal material was found offshore of the island for a distance of at least 100M, suggesting that the island has migrated landward with sea level rise. The area north and west of the island was very shallow, and historic channels were frequently not observable. Scattered lenses of oyster shells were found in this area. Creek mouths were very narrow and emptied into small embayments.9 Figure 5. Survey and probe transect core locations.

Sediment/soil analyses. The third step was to take soil cores and sediment dep ths along transects in order to determine soil types, origins, sequences and depths. Core locations are found in Figure 5 , with more detail found in Meeder et al . (2000) for the creek sites. Core descriptions are in Appendix A . Soil cores were collected in 8cm diameter aluminum core tubes using a simple piston coring device to minimize compaction. Compaction was measured for each core and was minimal except for fibrous peat at the creek sites. Soil profiles were described with special interest to the uppermost contact between the surface and immediately underlying soil types.

The basic soil types found were: 1) marl, 2) marly peat, 3) red mangrove peat, 4) black mangrove peat, 5) sandy mud, and 6) skeletal sand-gravel. Marls were not found at the surface in the study site. Marls are calcium carbonate (low Mg calcite, a stable mineralogy) produced by periphyton (Gleason, 1975). They form dense, impermeable sediments with either a freshwater or low salinity molluscan assemblage. Typical freshwater pulmonates are abundant in freshwater and the marsh clam, a cerithid, and abundant hydrobiids are found in the more saline marls. The more saline marls also tend to have much less organic material, a reflection of sparse Eleochariscover rather than denser Cladium

.10 A carbonate mud rich red mangrove peat (marly peat) rarely more than 10cm in thickness was found at the surface in small areas near the center of basins where mangrove cover was not complete. Within a marly peat horizon, the organic content increased upwards rapidly at the expense of carbonate mud (marl) content. Skeletal component was a fresh-to-low salinity mollusk assemblage. Fewer large Poliniceswere found than in the underlying marls. Most organic material was red mangrove root material with a secondary component of leaves locally.

Red mangrove peat was the most common surface soils in the wetlands and also in a small portion of the estuarine zone. Red mangrove peat was highly organic in nature (60% by dry weight or more), consisting primarily of root fibers (Meeder et al ., 1998). The mollusk assemblage was characteristically one of more saline to marine conditions. Fossils were usually few but included the marsh clam, Littorina
, Melampus , and cerithids. Near shore red mangrove peats may contain a marine mollusk fauna, because of onshore transport during storm tides.

Black mangrove peat differed from red mangrove peat in a black rather than red color, and the presence of pnuemataphores, as well as, root material as common soil constituents.

A gray to light brown, sandy mud with various amount of larger skeletal material dominated by a diverse marine mollusk fauna was the dominant surface sediment type in the proposed estuarine zone. In some locations near tidal creek mouths the marine mollusk skeletal component may be replaced by freshwater pulmonates from reworking and seaward transport processes.

Oyster gravels with a matrix of marine sand and mud form , thin, local lenses and one sizeable oyster bar were found. Most oyster skeletal material was fragmented with large single valves common. Double valves and small clusters of oyster shells were also found in some lenses and in the large bar (the island).

Vertical soil sequences recorded two basic, highly repetitive sequences. The first sequence was found throughout the coastal wetlands. In this sequence freshwater marl was replaced rapidly upwards into a transitional marly peat (from 1 to 10cm thick), and then to a surface red mangrove peat. In general, peats thinned away from the creeks and coastline. Peats thinned away from the creeks and coastline because the time for peat accretion decreased away from creeks and the coastline. This is indicative of a condition progressively becoming more saline with decrease freshwater discharge.

The second repetitive vertical sequence was found in the near shore area. In this sequence either freshwater marl, or more saline red mangrove peat, was overlain by marine skeletal rich sandy mud. The contact between the two strata was usually very sharp. The marine sandy mud was usually less than 40cm thick and frequently including thin (3 to 15cm thick) oyster skeletal lenses. Most oyster lenses, except the oyster barisland were buried by 15cm of marine sediments. This sequence represented an abrupt change from fresh water conditions to estuarine and then a more open marine salinity11 regime. The loss of live oysters was reflective of the lost of freshwater discharge as sea level has rose producing conditions too saline for oysters. Although mollusk assemblages can be used to determine paleosalinity, we did not differentiate assemblages beyond fresh and marine in this study because oyster paleoecology produced better, more precise paleosalinity data. Oyster paleoecology is addressed in the next section.

Distribution of surface sediment types in the coastal wetlands was rather simple. Red mangrove peat was found at the surface throughout almost all of the coastal wetlands. In the center of large basins where mangroves were not very dense, marly peat was found. In addition, black mangrove peats were found as thin shoestring deposits along old tidal creeks and behind the coastal levee in places.

Offshore of the fringing mangroves along most of the coastline was a thin marine mud or inundated red mangrove peat, which was exposed during most wet season low tides and most of the dry season. This narrow zone frequently had very little aquatic vegetation cover. The bottom deepened at a rather constant rate from the shoreline to the depth of approximately 125cm, where the water depth increaseed at a faster rate. This water depth increase is inversely related to the depth of sediment. Seaward of the narrow nearshore zone the surface sediments were mostly marine muds and sands between 0 and 45cm in thickness. North and west of the historic channel thin lenses of oyster shells were found as scattered patches. The maximum water depth was located in this earlier Holocene creek channel that was located approximately 100M south of the island. Basel sediments in this creek bed were highly organic, very dark brown to black marls with limestone clasts and freshwater mollusk shells. South of this ancient creek channel only patchy, thin sediments overlaid bedrock. Between the channel and the island approximately 45cm of sediment covered the bedrock. The surface sediments were marine muds and sands with a varying component of skeletal material up to 20cm thick. This overlaid and abruptly contacted either freshwater marl to the west and marl or mangrove peat to the north. The island was approximately 120M in length and 40M in width and was aligned in a southeast-northwest direction. The island was made up of oyster rich skeletal material overlaid by red mangrove peat. At high tide the island was almost totally inundated with the exception of the red mangrove tree cover. This island was first believed to be a dredged canal spoil bank. However, no channels were located anywhere near it, and the canals that were present along the mainland do not exhibit oyster shells along their banks or in adjacent soils. Furthermore, skeletal material was found offshore of the island for a distance of at least 100M, suggesting that the island has migrated landward with sea level rise. Creek mouths were very narrow and empty into small embayments.12 Figure 6

. Cross sectional depiction along north-to-south transect 1.

Depositional model. A depositional model is used to recreate historic topography. The model is based upon: 1) topography, 2) aerial photographic interpretation of changing plant distribution and plant cover/soil type relationships and 3) soil core transects. Topography is presented in Figure 4 . A time sequence of aerial photographs was assembled in order to document the distribution of vegetation and changes in plant (especially mangrove) distribution through time ( Figure 2 ). Two basic plant communities existed historically; red mangrove and gramminoid prairie marsh. The red mangrove forest produced a peat soil , the gramminoid prairie a carbonate marl soil. As mangroves replaced the prairie, the soil becomes more organic rich until the mangrove forest formed a continuous canopy which reduced and ultimately excluded periphyton in the prairie community and thereby stopped marl production. Using aerial photographs, the spread of mangroves and mangrove peats over different time intervals, and the thickness of the soil produced in each time interval along transect was determined (Figure 6 ). Mangrove peat thickness above the marl along the transect subtracted from the present topography gave us an approximation of the historic topography. A three dimensional soil surface map was then generated to display these changes allowing for analysis of rehydration feasibility. Almost all cores showed a red mangrove peat overlying freshwater marls with the overlying peats found in various thickness.

The coastline and tidal creeks were first exposed to marine conditions and mangrove propagules. As freshwater discharge decreased with time, the mangroves, and therefore mangrove peats migrated away form the tidal creeks producing a thinning wedge of surface peats ( Figure 6 ). By measuring the advance of mangroves away from the tidal creek at points documented in aerial photographs, and coring at these points, we established the rates of mangrove accretion. Marl accretion rates ranged from 1 to 2mm/yr. (Meeder et al ., 1998) and red mangrove peats approximately 5mm/yr. at this site. By 1972 mangroves had invaded and covered the entire wetlands. Therefore, in the13 center of the basin marls have been accreting for 44 of the last 72 years. The 1928 time line would then be 4.4 cm beneath the mangrove-marl contact. Over the period of this study, therefore, the basin topography has increased through time because of the faster rate of mangrove accretion over marls and mangrove peats have been accreting for a longer period of time along the creek margins than in the center of the basin.

Chronostratigraphy and serial aerial photography.Analyses (of a time series of aerial photographs: 1928, 1940, and 1992) documented major changes in vegetation patterns and coastal morphology (Figure 1 ) (Meeder et al ., 2000). Changes in vegetation patterns coincide with changes in soil type. This was documented by a series of soil cores along the 100M transect from the historic creek south into the historic prairie. Freshwater prairie with marl soils was replaced by mangroves and marly peats. Therefore, the contact between underlying marl soils and overlying peats were used as a time line. This is not the most precise method to define a time line as we recognize that the transformation from marl to peat occurred over a 15 year period. The shift started along the tidal creeks and expanded towards the basin center. Radiometric dating methods (Pb 210 and Cs) might provide a tighter time line but numerous problems and assumptions must be overcome. However, for the scope of this work the precision was adequate, and radiometric dating was very expensive for what it might add. Throughout the study area, including the nearshore bay, a more marine strata (ranging from 5 to 30 cm thick) overlaid a freshwater marl of mangrove peat. This contact, usually very distinct especially in the Bay, was considered a time line, which we placed at approximately 1935. A three dimensional depositional model based upon present topography and soil accretion since loss of fresh water delivery was produced. Four major changes were documented: 1) marsh marl soils were replaced by faster accreting mangrove peat soils, 2) loss of upper tidal creek channel morphology, 3) siltation and mangrove colonization of tidal creek embayment, and 4) abrupt change in estuary from non marine to marine sediments. Soil accretion rates were related to the type of surface community producing and/or modifying them (Meeder et al ., 1999). Freshwater marl rates usually accrete at the rate of 1 to 3mm/yr., sawgrass peats at 5 to 12mm/yr., and mangrove peat accretion rates can be much higher (Meeder et al ., 1996). Using aerial photographs from different years we documented the spread of mangrove and mangrove peat with increased saltwater encroachment. When sites along this gradient were cored, the thickness of mangrove peat overlying freshwater marl was consistent with most mangrove annual accretion rates (Parkinson et al ., 1993; Meeder et al ., 1996). Thereafter, the contact between the peat and underlying marls were used as a time line with the understanding that this time line actually spreads over a time period of approximately 30yrs. However, this approach is not as unreasonable as it first seems, because the underlying marl accretion rates are an order of magnitude lower than the mangroves. Therefore, very little preexisiting topography will be missed by this approach.14 Figure 7

. Three-dimensional topography/bathymetry map illustrating the elevation differences between historic and present conditions.

Historic topography/bathymetry. Historic conditions were established using serial aerial photography and soil cores along transects to determine paleotopography ( Figure 7 ). As freshwater discharge slowed and then stopped, the rate of saltwater encroachment was proportional to the rate of freshwater discharge decline and stoppage. As saltwater encroachment increased so did the expansion of mangroves over the previous fresh water marl prairies. Soil core transects across this trend documented a surface layer of mangrove peat overlying marl that thinned away from the tidal creeks. Because marl accretion is 5 to 10 times slower than mangrove peat accretion the contact between peat and marl is used as a time line with minimal error over the period of this study (1928 to present).15 Figure 8

. Historic contours and bathymetry.

DISCUSSION

Present wetland morphology prevents direct rehydration of the historic tidal creek because of mangrove peat soil accretion in tidal channels west of the point of present tidal exchange. Freshwater flow and tidal exchange prevent siltation and loss of channel morphology. The release of freshwater into the system probably will not result in instant reestablishment of the abandoned creek channel for three reasons. First, as mentioned already, the tidal creek channel morphology is gone. The topographic basin south of the creek is more pronounced at present than in 1928 because of the greater rate of mangrove peat accretion than that of the marl soils in the basin, which has resulted in much higher channel levees than those of the past. Finally, an old, poorly defined sloughway, or series of marsh depressions, are located near the center of the basin close to the east-to-west survey line (visible in the 1940 aerial photograph) and will probably capture the water. Water will pile up until it overflows the mangrove peat basin margin and erode downwards forming a new channel. Another probable scenario is that the water will pile up in the basin until the lowest spot in the basin margin is found; a likely spot for this to occur is along the abandoned creek at about 250M east of the levee of along the ditch lying along the southern margin of the basin. The capture of the basin water by the ditch is the least desirable scenario. The reestablishment of a creek morphology from the levee16 to the Bay may take a few years to become reestablished depending upon the freshwater discharge. The more discharge, the faster channelization will occur.

The small embayment at the tidal creek mouth has been reduced in size and depth by siltation and mangrove colonization. Since 1940, the mangroves have accreted as much as 40 cm of peat over the embayment muds and freshwater skeletal remains deposited there by freshwater out flowing currents from the marl prairies. Reestablishment of the embayments is not likely in areas with thick mangrove peats. However, the shallow open water areas of the embayment might be scoured and transported into the Bay with sufficient reestablished freshwater flow. However, the freshwater retention capacity of our proposed estuarine zone has been irrevocably diminished in the areas of peat accretion.

In conclusion, historic changes in the wetland and nearshore Biscayne Bay area are documented, and these changes appear to minor enough that rehydration of a tidal creek system probably will not be curtailed but may take a few years to reach a new equilibrium between erosion, deposition and water flow patterns.

Changes in topography/bathymetry. The major reason historic conditions were addressed was to determine if conditions have changed so much that reestablishment of an estuarine zone would be impossible. Although numerous changes are documented between present and historic conditions freshwater delivery should be able to reestablish estuarine conditions. The only concern is whether canal water discharged into the study block will develop channel flow once again or will spread out into sheet flow. If enough water is delivered we feel that channel flow can be established within a year or two. The desirability of channel flow over sheet flow is that much less water will need to be delivered to meet the target salinity than if sheet flow is the major process. The new creek channel is likely to develop approximately 100M south of the historic channel in the present center of the depression. As the depression fills channelization will probably occur through the first breach (old tidal creek channel, many of which are still present in reduced form 300 to 400 M inland from the coast). In other words, the lowest spot along the margin of the topographic depression. Several such depressions exist, to the north of the depression (the historic creek channel), east to the series of abandoned tributaries, or southeastward to the manmade ditch that crosses a historic channel. This last situation is the least desirable, because it would deliver water too far south of the proposed estuary, south of the oyster island, and might not stay in the system as long as delivered further north. In addition, the straight man made channel would be more efficient in water delivery but would not carry as much mangrove detritus.17 PART 1: SALINITY

Historic changes in salinity and the effect on the coastal wetland-nearshore ecosystem were documented. Three methods are used in this documentation: 1) chronostatigraphy and serial aerial photography, 2) biogeochemical salinity markers, and 3) invertebrate, especially oyster, paleoecology. In summary, all evidence suggests a decrease in freshwater discharge associated with an increase of wetland and coastal salinity. To accentuate the loss of freshwater discharge, a rise in sea level of approximately 20 cm has occurred during the last 100 yrs (Maul and Martin, 1993). As conditions became more saline, the nearshore estuarine zone was lost as was the oyster (Meeder et al 1999) and estuarine-based fisheries (Serafy, 1997). Oysters have rather specific habitat requirements and therefore oyster paleoecology was used to determine historic salinity.

A. Oyster distribution at the study site . Sediment probe transects and soil cores demonstrate the abundance of oysters over a rather large area with a concentration found in a NW to SE trend. When discussing oyster shells we are restricting our discussion to level bottom Crassostrea virginicaand not mangrove root encrusting forms. The two forms can be separated easily by overall shape of the shell, especially the shape of the post settlement and young adult stages shell attachment area (Stenzel, 1971).

1. Present live oyster distribution . At present, live oysters were only found living on mangrove roots along the shoreline and up the tidal creeks for a distance of approximately 100m. Oyster and barnacle density on the roots were low, rarely covering more than 30% of the root surface in areas where the roots were always subtidal. However, spat attachments and one-year age class oysters were the norm and larger oysters were very uncommon. The occurrence of live oysters, however sparse, does indicate that oyster larvae were present.

2. Distribution of dead oyster shells . Dead shells were found in several settings: 1) at the base of mangroves, along tidal creeks with fell after death from their attachments on prop roots, 2) throughout the estuarine zone north and west of the island, 3) from the island southward approximately 150M and eastward 100M below a thin marine sediment layer (0 to 20 cm thick), 4) small discontinuous lenses along the tidal creek banks below a surface marine sediment layer (5 to 20 cm thick), and 5) the island in the estuary is basically constructed of oyster shells, many if not most, were disarticulated but small clumps were common. Many small clumps were overturned as an indication of transport. The oyster shells appeared to be concentrated above a freshwater marl or mangrove peat north, west, and southeast of the island, freshwater marl to the southwest and south of the island ( Appendix 1 ). The oyster bearing strata away from the reef contained mostly single valves which is indicative of transport. However, throughout the strata occasional oysters with both shells and small clumps were found implying that random spat fall was successful but did not develop further at this site. Oysters do not have a “hard hinge”, and therefore disarticulate soon after death18 when not held together by encrusting organisms or buried by sediment. The island itself overlaid mangrove peats. The island in the estuary zone was at first thought to be dredged material. However on closer inspection, no channel existed on either side of the island, the adjacent dredged canal to the west did not have any outcropping oyster shell, and the island had an offshore trend (see 1940 photo).

3. Oyster deposit interpretation

. a. Sea level has risen approximately 20cm in the last century. Combined sea level rise and hurricane erosion was responsible for 25m of coastline retreat and the submergence of the oyster facies seaward of present coastline because of transgression and overstep. b. Frequency of high energy events also redistributed oyster shells from the reef facies. Three major hurricanes have passed over this part of the Biscayne Bay shoreline in the last century. c. Fossil oysters were found as 1) transported debris characterized by thin, discontinuous lenses of disarticulated shells not in life position, 2) sparse individual oysters or small clumps in growth position randomly scattered, 3) wedge shaped oyster shell deposits along the creek banks (predominantly comprised of coon oyster debris), and 4) thick lensoidal deposits including skeletal debris and small clusters, some of which were in life position. This latter was the mangrove covered island. The oyster deposits were covered by red mangrove peat and the oysters were exposed only at low tide. The island has undergone modifications from high energy events ( Figure 3 ).

B. Oyster paleoecology. Oysters are one of the most studied marine animals with a literature dating back to at least 1665 (Joyce, 1972). This is no doubt because of the economic significance of the oyster as a foodstuff, a nursery ground for numerous other estuarine organisms, and the navigation hazard oyster reefs, or bioherms, pose to nearshore craft. The earliest studies of oyster distribution documented that their preferred location, especially true for bioherms, was between the freshwater and marine environments. Presently, this zone is usually referred to as an estuarine or brackish water regime. Numerous studies document the specific conditions that oysters live in from New England to Mexico. The generally agreed to environment is one of brackish salinities, near river mouths or other sources of organic particulate matter, the presence of water currents sufficient enough to prevent siltation of the bioherms or individual oysters, and generally within the depth range of one foot above mean low tide to 60 ft. Intertidal oysters differ from subtidal bioherms by the greater stress of exposure (temperature extremes and desiccation).

The oyster of concern, Crassostrea virginica , is found from the Gulf of St. Lawrence to Biscayne Bay, Florida along the Atlantic coast continuing along the Gulf of Mexico to the Yucatan Peninsula, Mexico (Gunter, 1951). Southeastern U.S. oysters, Crassostrea virginica , are well-studied commercial shellfish, which also are well preserved in the geological record. C. virginicais a euryhaline species found singly in conditions ranging from near freshwater to normal marine salinities. Oyster reefs, or more properly19 bioherms, are much more restricted in their distributions. Temperature, predation, water circulation, larval period and settlement requirements, and tidal range also greatly affect oyster reef growth and distribution.

The factors controlling oyster development and distribution include:

1. Salinity . Although euryhaline in nature, C. virginicabioherm development usually occurs either in intertidal areas or subtidal areas of reduced salinities. Neither eggs nor functioning spermatozoa develop unless salinities exceed 7.5ppt whereas larvae and young adults find optimal conditions at 17.5ppt, although tolerating 10 to 40ppt (Stenzel, 1971).

The relationship between oysters and the low salinity estuarine habitat was recognized very early in South Carolina (Dean, 1892), Georgia (Oemier, 1894), Mississippi and Alabama (Ritter, 1896), North Carolina (Grave, 1905), and Florida (Pearse and Wharton, 1938). The significance of the salinity range to oyster presence and development is believed to be related to the paucity of oyster parasites and predators in low salinities (Grave, 1905, Gunter, 1955).

Oyster spat successfully develop in waters of greater than 5ppt. Young and adult oysters can maintain freshwater for up to 10 days by closing their mantles tightly and storing water. The length of time for successful exposure to freshwater appears to be the amount of energy stored in the oyster tissue.

2. Temperature

. C. virginicacan tolerate a temperature range from –2 to 30 o C. Subtidal oysters can withstand the extremes better than intertidal individuals. Spawning is reduced or eliminated as temperature decreases. Mature oysters can live in freezing conditions for long periods of time but in the colder portion of their range oyster occurrence is dependent upon larval recruitment. Southern oysters grow faster than northern ones but are more subject to death in sudden freezes (Menzel, 1951).

3. Predation. Grave (1905) documented that oysters are subject to higher rates of predation and parasitism with increased salinity. Gunter (1950) suggests that this is a response to his documentation of a general increase in marine diversity with increase salinity. This is particularly true when considering that the brackish water fauna is derived almost exclusively from marine stock. In our area, there is frequently one exception, the estuarine hydrobiid. However, this may be considered incorrect because the hydrobiids are a group of mesogastropods that have secondarily become adapted to freshwater conditions. Wells (1961) studied the relationships of oyster fauna along a salinity gradient in Beaufort, North Carolina. He found the biggest break in species diversity between stations at Galliant Point (28ppt) and Cross Rock (19ppt). In addition, numerous predators and parasites were excluded between Write Rock (24ppt) and Cross Rock. Many predators and parasites while not excluded at 19ppt were found in very reduced numbers or only during periods of elevated salinity.20 4. Feeding.Oysters are passive, sessile, filter feeding organisms which capture particulate organic detritus and algae. Loosaneff (1962) determined that feeding activity is highest at low food concentrations.

5. Water circulation (siltation and suspended food supply). Oysters are suspension feeders and require water current to both 1) carry and retain in suspension organic detritus as the primary food source and 2) to prevent siltation and burial of the oyster. Therefore, oysters tend to form positive relief features at or near river mouths and on the high-energy side of tidal creeks.

Siltation of oyster ecosystems occurs frequently after both large flood and hurricane storm tides. Both events cause considerable bottom erosion and redeposition of vast amounts of sediment. These events happen episodically and the reef system usually responds to burial by permanent death, shifting laterally, or by recolonization of the new surface. These events have been recorded in Texas, Mississippi, Louisiana, Apalachicola, Florida and other areas.

6. Larval period and settlement requirements . The larval life stage ranges from 7 to 10 days, but some larvae remain planktonic for up to two months in cooler periods or when food is not abundant (Bahr, 1981). Oyster larvae are usually present from April through October. This period coincides with the rainy season in South Florida, which is the period of highest daily and spring tides. The free swimming larval stage is reduced in warmer climates. South Florida oysters are 25 o C spawners (Yonge, 1960).

7. Tidal range . Most well developed oyster bioherms occur in areas that characteristically have a tidal range exceeding 1 M. In areas of intertidal oyster bioherms, exposure increases stress from temperature at both extremes but also offers protection from many predators that do not tolerate exposure. The height of intertidal oyster bioherms decreases with decreasing tidal amplitude. In South Florida, the development of intertidal oyster bioherms is impeded by the microtidal range, as well as the presence of more carnivores.

In summary, the two most important factors controlling oyster development are a proper salinity regime and steady food bearing water currents.

C. Oyster bioherms. 1. Structure . Previously discussion revealed that oyster bioherm distribution and structure are related to physical parameters and the supply of suspended organic detritus. Butler (1954b) reports types of subtidal oyster accumulations based upon their location in an estuary ( Table 1 ). He found that location of the oyster in the estuary was most influenced by salinity regime. As salinity increases towards open water species diversity increases and with increased diversity, parasitism, predation, and fouling increase which influences the survivorship of oyster spat and oyster growth morphology.21 Table 1

. Characteristics of four categories of oyster reefs. Location Shell characters Salinity Range (ppt) Salinity Mean (ppt) Diversity Oyster abundance Spatfall Fouling and predation 1 Estuary Head Small, round, smooth, little clumping 0-15 10 Low Sparse Low Low

2 Midestuary Smooth, narrow, dense, w/small clusters 10-20 15 Moderate Max High Low

3 Near estuary mouth Massive, eroded w/ heavy, concentric ridges 10-30 25 High Dense Highest High

4 Junction of estuary with bay Large, highly eroded and ridged 20-35 30 high sparse Low Highest

Bahr and Lanier (1981) report the distribution and characteristics of intertidal oyster reefs in a tidal creek system and discussed reef development. Oyster reef development has four stages; 1) colonization, 2) clustering phase, 3) accretionary and 4) maturation and senescence. Briefly, the colonization stage occurs as spar find successful places to settle and form an area of single live oysters and a few small clumps. The clustering phase occurs when several successful generations of spat create clusters with two to eight generations of oysters with the base of clusters mostly dead shells. The oyster accumulation still expresses very little relief. The accretionary stage occurs after additional spat fall closes the gap between clusters and the reef begins to expand vertically and laterally. At this stage most reef are approximately one meter in thickness (where tidal range permits). A mature or senescent stage is reached when the reef grows to the surface where exposure limits vertical growth.

Within the tidal creek system oysters colonize where water currents provide a clean substrate for spat settlement with low sediment deposition rates. Locations favored for reef development include: 1) along the concave outer banks of meander loops, 2) in areas immediately adjacent to smaller tidal tributaries, and 3) at points of tidal creek confluence (Bahr and Lanier, 1981).

2. Oyster Bioherm Distribution. The southernmost oyster bioherm in the United States is in Oyster Bay, Everglades National Park (Tabb et al ., 1962). Distribution of dead oyster shells and buried shell deposits suggest that the bioherm was much larger than present in the recent past. The oyster bioherm is exposed during low spring and most neap tides (Tabb et al ., 1962). Recovery of the bioherm has been rapid after severe impacts by hard freezes and hurricane impacts. The oyster community was species poor. During winter dry periods as water salinities increased, the bioherm was overgrown by the algal species; Gracilaria
, Laurencia , and Acanthophora spicifera . The nearest salinity stations22 are approximately one mile northwest of Oyster Bay (low salinity of 12, high of 37.6 and a mean of 28.1ppt) in Whitewater Bay XII near the mouth of the bay and approximately two miles southeast (low salinity of 2.2, high of 38.7 and a mean of 17.9) at White water Bay VII. Oyster Bay salinities should be closer to Station VII than XII because of different geography and freshwater discharge patterns.

Turney and Perkins (1972) report that C. viriginicawas abundant in 25% of their benthic sites in northern Florida Bay. They did not sample oyster bioherms or tidal creeks. This region they referred to as the Northern Sub environment which they characterized: salinity range 13-48ppt, Temperature range 15-38 o C, restricted circulation with little tidal activity, and subject to severe freshwater runoff events. The characteristic species in this sub environment is Anomalocardia cuniemerisfollowed by the following common species: Parastarte triquetra
, Melongena corona
, Retusa cacaliculata
, Rissoina browniana(probably R. fisheri ). Other species were also common but more abundant in the interior subenvironment (also with low salinities) are Brachidontes exustus , Pinctada radiata, Cerithium muscarum
, Bittium varium, Modulus modulus
, Lucina multilineata
, Olivella sp . Most of these species are associated with the present oyster fossil assemblage.

Generally, the oyster habitat in southern Florida /Florida Bay region is located below low water in the intertidal mangrove zone along creek bank prop roots and less frequently along high energy tidal creek banks and as bars in tidal creeks. Tabb et al . (1962) report that the abundance of oysters decreases away from Oyster Bay both to the west towards the mouth of the estuary with the increase in salinity, and to the eastward where salinities range from 0 to 15 ppt. This delineates a range of 5 to 20 ppt that may be the optimal for C. virginicain South Florida. This range is supported by studies in Applicacola Bay, Texas, Georgia and the Carolinas as previously cited.

Oyster bioherm have been reported permanently killed by increases in salinity associated with levee construction that prevented freshwater from reaching estuaries in the lower Mississippi River (Gunter, 1952). Construction of deep water navigable channels usually results in saltwater intrusion and increased salinities, for example Calcasieu Lake and Atchafalaya Basins, Louisiana (Van Sickle, 1972).

D. Biscayne Bay and study site oysters . Harlem (1979) reported extensive oyster shell beds in Northern Biscayne Bay. Little literature reports oysters in central and southern Biscayne Bay. However, oyster bioherm strata were mapped in 9 of 48 tidal creeks along western Biscayne Bay (Meeder et al ., 1999). Most tidal creeks where oysters were present were located at tidal creeks that began as freshwater sloughs. None of these historic oyster beds were active. At our present study site oysters were distributed over most of the Bay bottom as a thin lens, as a large single reef, and along some creek banks. Throughout the study area the oysters appeared to have died off within a short period of time, and were subsequently buried by marine sediments.23 They overlaid fresh to brackish water sediments. The die off was associated with the loss of freshwater discharge via transverse glades-tidal creek systems. The loss of freshwater discharge produced three major changes in the system responsible for the loss of living oysters; 1) rise in salinity, 2) decreased particulate organic carbon load and 3) increased siltation rates. The loss of freshwater discharge probably started after the turn of the century associated with dewatering of the Everglades. All sheet flow to the Bay was lost by the construction of the L31E system in the 1960’s. In addition to increased salinity (and associated increase in parasitism and predation) and decreased food supply, water quality has decreased with the addition of anthropogenic sources of nutrients. The increased nutrient loading to the Bay has resulted in the nearshore zone frequently being overgrown with filamentous algae. An algal cover on the substrate may reduce successful larval recruitment and interfere with oyster filtration processes (Redfield, 1952; Lund, 1957). A salinity increase could be associated with decreased groundwater discharge because of a loss of between 4 to 6 ft of hydraulic head due to drainage (Parker, 1975). This scenario has been reported for the Duplin River, SC (Kjerfve in Bahr, 1981). The failure of oyster reefs because of increased salinity has been reported from numerous locations and is quite likely the major problem at this site. Bahr (1981) suggested that in most regions, an increase in salinity has more serious implications for oyster reefs than moderate levels of nutrient loading.

Oysters at the historic creek site developed through the clustering phase and probably no further because of the microtidal range. Because the tidal creeks emptied directly into Biscayne Bay without an embayment or restricted exchange, oyster distribution and development was somewhat different than in most places. Oysters were most abundant at the mouth of the tidal creek which has since been stranded by shoreline erosion.

In conclusion, the presence of oysters was indicative of salinities ranging between 5-20ppt, and continuous water current, which brought particulate organic carbon and prevented siltation. Small-scale oyster structures were indicative of the microtidal range, occasional freezes, and hurricane energies, which limited growth and maintained early successional stages of oyster reef development. The loss of oysters in this situation was the likely the result of the loss of freshwater discharge, which permitted salinities to rise. With increased salinities, increased predation, parasitism, and fowling organisms reduced oyster survival. In addition, the loss of freshwater flow reduced particulate organic carbon available and allowed siltation to occur. When oysters were lost, nutrient loading probably was not a causative factor, however with today’s high nutrient loading rates oyster recolonization and bioherm development may be retarded.24 PART 2: FRESHWATER DISCHARGE (Q) MODEL

The major objective of this model was to estimate the volume of water required to meet nearshore Biscayne Bay salinity targets. The water to be discharged via the L-31E canal into a historic creek watershed empties into Biscayne Bay, just south of a prominent point, approximately 400 M north of Military Canal ( Figure 9 ). Historically, freshwater discharge was sufficient to provide a salinity regime that supported accumulations of the bay oyster, Crassostrea viriginia(Meeder et al ., 1999) and numerous estuarine fish species ( Serafy et al
., 1997). The salinity regime determined to be adequate for the establishment of an estuarine zone was: Wet season (5 to 15ppt) and dry season (10 to 19ppt). The following model was based upon estimates of numerous parameters, including biological, climatological, physical, bay water circulation, and others, and was summarized in Table 2 . More detailed sections on each parameter follow the table.

Figure 9

. Schematic model of study areas illustrating the major processes.25 Table 2

. Summary of model parameters. Volumes were calculated under normal spring tide conditions unless otherwise noted. Sources and calculations follow. Parameter Dry Season Wet Season Units Comments

A. Target salinity 10 to 19, mean of 15 5 to 15, mean of 7 ppt Max of 20

B. Bay Salinity 25 15 ppt Max 36 C. Marsh area M2 551,700 D. Wetland basin volume 9,557 53,702 M3

E. Estuarine basin area 65,500 81,700 M2

F. Estuarine Basin volume 20,445 42,525 M3

G. Tidal volume 14,445 29,302 M3 H.Wind:direction speed 340 9.3-10.1 120 7.9-10.6 Compass degrees mph 2.26 5.74 7.18 18.23 in/mo. cm/mo. Annual=56.1in over 29 yrs I. Rainfall: Miami Tavernier 1.93 4.9 5.6 14.22 in/mo. cm/mo. MW= Annual = 44.8in over 29 yrs J. PE 6 5.5 2.5 2.3 Mm/d L/M2 /d MW=1268.9M 3 / d MD=3034.3M3 /d BW=187.9M3 /d BD=449.4M3 /d Duever et al., 1979

1.74-2.05 L/M2 /d 2,758.5M 3 /d K. Transpiration Dwarf mangroves Fringe mangrove 8.6-11.8 L/M2 /d Ross et al. ,1999 (p. 38)

L. Groundwater discharge: 50M 200M 0.03 0.105 M3 /M2 /d M3 /M2 /d For study area 2084M3 /d 19,850M2 rock bottom

M. Water table elev. 1’7” 2’1” SFWMD schedule

N. Military to Mowry Bay vol. 503,125 568,750 M3

O. Military to Mowry bay tidal volume M3 131,250

P. Estimated renewal time 2.5 1.5 d

Q. Estimated required freshwater discharge 10 15 M3 /d

Acre-ft.26 A. Target salinity. Seasonal target salinity ranges and means were determined in Part 2. In summary, target salinities were based upon oyster paleoecology. Wet season nearshore salinities should range between 5 and 15 ppt with a desirable mean of 7 ppt, whereas dry season salinities should range between 10 and 19 with a mean of 15 ppt. Maximum salinity target should be 20ppt.

B. Bay Salinity.The nearshore area of western Biscayne Bay was subjected to seasonal salinity changes. The nearshore area was defined as the area within 100M of the shoreline and usually less than 1.3M in depth. Salinity was measured every month at two sites between the Military and Mowry Canals for five years (Figure 10 ). This water was a mixture of Mowry Canal discharge and open Biscayne Bay waters (approaching normal marine salinities). This mixture, ranging from near fresh to 30 ppt, formed a plume that traveled northward along the coastline most of the year, and was the source of bay water reaching the present historic creek site. Therefore, in modeling for target salinity, we used these seasonal values rather than 35ppt for normal seawater. There was no significant difference in salinity between the two bay stations (CBB and TBB), which are about 1km apart. However, there was an obvious difference between the dry season salinity mean (approximately 25ppt) and the wet season salinity mean (15ppt). The strong break between the end of the dry season and the beginning of the wet season (June) was also very apparent ( Figure 10 ).

0 5 10 15 20 25 30 35 40

Jan Feb March April May June July August Sept Oct Nov DecSalinity (ppt) Year 1 CBB (1996) Year 2 CBB (1997) Year 3 CBB (1998) Year 4 CBB (1999) Year 5 CBB (2000) Year 1 TBB (1996) Year 2 TBB (1997) Year 3 TBB (1998) Year 4 TBB (1999) Year 5 TBB (2000)

Figure 10

. Nearshore salinity from two stations just south of the Historic Creek site.

C. Wetland area and relief.The area of marsh involved in this project was determined by planimetry based upon a 10M 2 grid ( Figure 11 ). Topographic27 relief was mapped by the use of several survey lines and field observations (Meeder et al ., 2000).

Figure 11

. Displays the marsh topography (contour interval 2.5cm) and the estuarine zone bathymetry (depth contour intervals 0.3M). The bathymetry is based upon normal spring tide water depths that flood the marsh by 20cm near the coast.

D. Wetland basin volume. The volume of water required to flood the coastal mangrove wetland east of the L-31E canal with up to 15 cm of water (a normal wet season spring tide flood depth) is 53,702 M 3 . This was based upon planimetry of areas of similar elevation using a 5cm contour interval and assuming a uniform slope ( Figure 11 ). The assumption of a uniform slope permitted the volume calculation using one half of the contour interval. This approximated conditions at the site in most areas, except around tidal creeks, shoreline, and just behind the coastal levee. A normal summer spring tide inundated most, but not all, the wetland surface. A water depth greater than 20cm was unusual except in local areas around old abandoned tidal creeks and near the coast behind the coastal levee. A normal dry season spring tide rarely flooded more that half of the wetland surface (0.425cm). Therefore, flood volume was equal to III + IV in Table 3 on 9,557M 3

.28 Figure 12

. A schematic model that illustrates the method used in calculation of wetland inundation volume. The critical data used in the calculation are summarized in Table 3

.

Table 3 . Summary of area and volume of wetland by elevation increments. Depth increment (M) Units Area (M 2 )=units x 100 Volume (M 3 ) 0.525 to 0.475 445 44,500 26,473 0.475 to 0.425 3075 307,500 17,672 0.425 to 0.375 1084 108,400 7,275 0.375 to 0.325 93 9,300 2,282 TOTAL 469,700 53,702

E. Estuarine basin area and bathymetry . The estuarine area was calculated in the same manner as the wetland. A 10M grid was overlaid on the aerial image, bathymetry lines drawn for typical depths at spring high tide, and squares counted using standard methods. The bathymetry was originally taken from USCGS chart29 for Biscayne Bay but lacked detailed inshore data. Several wading transects were made at high tide ( Figure 5 ). These same transects were used for soil probing and core sampling.

The predicted nearshore area to be impacted by this rehydration of a tidal creek was 81,700M 2 . A bathymetry map, at normal high tides that inundates an extensive mangrove swamp by up to 15 cm, was produced ( Figure 7 ). The area flooded during the dry season was approximately 65,500M 2 . This calculation was based upon the average dry season spring tide elevation which was approximately 0.3M lower than during the wet season.

F. Estuarine basin volume. The volume of the estuarine zone was calculated in the same manner as for the wetland flood volume ( Figure 13 ). The only difference was that the bathymetry contours were in 30cm increments. Data used in calculation of wet season spring basin volume by water depth increment were summarized ( Table 4 ).

Table 4 . Summary of basin data used in volumetric calculations by depth increment. Depth increment (M) Map units Area (A=map units x 100M 2 ) Volume (M 3 )

0 to 0.3 162 16,200 22,080 0.3 to 0.6 347 34,700 14,445 0.6 to 0.9 262 26,200 5,310 0.9 to 1.2 46 4,600 690 TOTAL 81,700 42,525

Wet season spring tide volume was 42,525M 3 . Dry season volume was calculated in the same manner, however, dry season spring tides were approximately 30cm lower than in the wet season. Therefore, dry season volume was equal to II + III + IV or 20,445M 3

.30 Figure 13 . A schematic model that illustrates the method used in calculation of estuarine basin volume.

G. Tidal volume. Tidal volume for the nearshore basin was determined using a wet season spring tide range of 45cm and dry season tidal range of 30cm. The wet season tidal volume was equal to the sum of depth increment one (I) and one-half depth increment two (II) ( Figure 13 ). Not only were dry season spring tides lower than wet season spring tides, but also the height of the high tide in the dry season was approximately 30 cm lower than the maximum normal spring tide during the wet season. Therefore, dry season tidal volume approximated the volume for the depth increment two (II) (Tide tables for South Florida, USCGS and short term water level recorders (Ross et al. , 2000)).

H. Wind direction . Wind data were provided by The National Climatic Data Center. The following data was collected at Miami International Airport (MIA) for a period of 44 years for wind speed and 28 years for wind direction. Data provided were monthly means ( Table 5 ).31 Table 5 . Summary of wind data at Miami International Airport. Record Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr.
Wind 44 9.5 10.1 10.6 10/6 9.5 8.2 8.1 7.9 8.3 9.3 9.7 9.3 9.3 Dir. 28 340 340 120 120 120 120 120 120 90 70 90 340 120 Wind =mean monthly wind speed (mph); Dir. = Prevailing wind direction.

I. Rainfall and temperature. Rainfall was hard to estimate along the coastal zone from inland rainfall stations. This was due to the fact that daily convection rainfall usually did not drop until clouds reach a temperature change over land. This usually occurred several miles inland. Rainfall was almost always less per event than inland records indicate unless rainfall was associated with large fronts or depressions. Therefore, we chose to utilize the Tavernier rainfall data over the Miami Airport data set ( Table 6 ). A visual comparison between the two stations suggested that dry month rainfall varied less than wet season rainfall, which was mostly convection and depression rainfall.

Table 6 . Monthly means of temperature ( o F) and rainfall (in.) for Miami and Tavernier, Florida. 29 yr. record. Miami Tavernier Month Ave temp. Rainfall Ave. temp. Rainfall Jan 67.3 2.01 69.5 2.18 Feb 68.3 2.08 70.1 1.96 Mar 71.8 2.39 73.7 1.7 Apr 75.2 3.03 76.7 2.0 May 78.6 6.21 79.8 4.54 Jun 81.3 9.33 82.2 8 Jul 82.8 5.7 84.1 3.28 Aug 83 7.58 84.2 4.5 Sep 81.9 7.63 82.9 6.25 Oct 78.3 5.64 79.4 6.01 Nov 73.4 2.66 75.1 2.6 Dec 69.1 1.83 71.1 1.79 Annual 75.9 56.1 77.4 44.82

J. Evaporation. Data on evaporation came from the Big Cypress Swamp, SW Florida (Duever et al., 1979) and for Hialeah and Tamiami Trail Stations (Florida Climate Center).32 Table 7

. Evaporation rate data summary. Station Hialeah Tamiami Trail Big Cypress in cm L/M 2 M 3 total in cm L/M 2 M 3 total cm L/M 2

Wet

season Mn 6.325 16.06 5.05 12.83

D 0.54 5.4 0.43 4.3 0.25 2.5 Dry

season Mn 5.02 12.75 4.16 10.57

D 0.43 4.3 0.35 3.5 0.6 6.0 High tide bay flooded area = 94,400M 2 , low tide area = 49,800M2

K. Transpiration. Mangrove transpiration rates were measured just south of this study site (Ross et al ., 2000). As mangrove biomass increases so does transpiration, consequently, little seasonal difference was determined. Dwarf mangrove rates varied between 1.74 and 2.05l/M 2 /day in contrast to the fringe mangrove sites, which ranged between 8.6 and 11.8 L/M 2 /day. In the historic creek study area, the scrub mangroves were much higher and denser than at the previously studied areas. The fringe zone is narrow and located along the coastline and along the major tidal creeks for a maximum distance of 250M. Therefore, we selected an average of 5 L/M 2 /d as a reasonable average for the entire marsh site. Using that average, we calculated a daily water loss from the marsh of approximately 2,758.5M 3 /d by transpiration processes.

L. Groundwater Discharge. Meeder et al. (1997) documented significant groundwater discharge to nearshore Biscayne Bay. Fifty meters from shore the average groundwater discharge was 0.03 M 3 /M2 /d and at 200M from shore 0.105M 3 /M2 /d. This study was completed approximately 1 km south of the present study site and should be applicable. No significant seasonal differences were observed in groundwater discharge at the shore or at 200M offshore. Although the groundwater table was managed seasonally, the head difference either was not sufficient to produce different discharge rates or, the coincidence between managed lower groundwater levels and lower tidal heights in the winter mitigate one another.

Most of the bay bottom was covered by a dense fresh water marl which is impermeable, or nearly so, and therefore groundwater discharge was negligible. However, approximately 19,850 M 2 of bay bottom south and southwest of the island is exposed bedrock. Therefore, we determined groundwater discharge for the estuary by using the area 19,850 M2 and a discharge rate of 0.105M 3 /M2 /d. This rate was used (200 M offshore data) for the entire area because of the lack of overlying sediments which reduced groundwater discharge (Meeder et al ., 1999). This was a conservative figure based upon application of Darcy’s Law that predicted groundwater discharge decreased exponentially in the offshore direction. In our previous study of groundwater discharge, the 50M offshore33 discharge was lower than 200M offshore stations because of sediment overburden in the inshore area. Therefore, we estimated 2084M 3 /d.

Figure 14. Relationship between groundwater flow, distance from shore, and season.

M. Water table elevation. The groundwater stage was regulated by schedule using large water control structures near the mouths of major canals and the coastal protection levee and canal (L-31E). Between May 15 and Oct 15 (the wet season) the water table was managed at 2’1” and from Oct 16 to May 14 (the dry season)

N. Military to Mowry Canal near shore Biscayne Bay volume. The volume of water, at spring high tide during the wet season, from the shoreline to 1.3M depth (approximately 500M) offshore between the Military and Mowry Canals (approximately 1750M), was approximately 568,750M 3 . Dry season volume was 503,125M 3, and was based upon a depth of 1.15M, because winter spring tides were generally lower than summer and fall spring tides. This calculation assumed that the bottom gradient was uniform. Tidal volume was approximately 131,250M 3 /cycle, based upon a 30 cm tidal range.

O. Estimated nearshore water renewal time. Water renewal time is a measurement of the time required to totally replace the water in a basin. To obtain target salinity, a balance between freshwater discharge and mixing with seawater was necessary. The amount of freshwater required was dependent on how fast the freshwater mixed with seawater, and the rate at which water left the basin.34 Estimates of renewal time can be observed by watching the length of time freshwater remains after a major runoff event or, the reverse, how long the bay stays saline after a dry spell is broken. The observed rates in Biscayne Bay were quite fast compared to most estuaries. The small size and volume of the basin, the shallowness, and the lack of a restricted mouth or inlet to the bay permitted fast mixing and export. Estuarine zone water renewal time was calculated by estimating the tidal volume lost to the zone each tidal cycle, multiplied by two because of our characteristic diurnal tide patterns. This was the volume that must be replaced each tidal cycle from either freshwater discharge or incoming bay water. We could, therefore control the estuarine zone salinity by changing the volume of freshwater discharged.

Wet season tidal flow patterns documented that approximately 33% of the tidal volume of the estuarine zone moves northward because of prevailing SE winds and was lost to the estuary ( Figure 15A ). Approximately 66% of the tidal volume moved offshore each tidal cycle but returned to the estuarine zone. Therefore, 33% of the estuarine tidal volume was replaced each tidal cycle by a combination of bay water and freshwater discharge. Because of wind forcing processes, more tidal water exited north of the island than came in with rising tide. During the start of dropping tides with a SE wind, the tidal water mass separated at the head of the channel south of the island and part moved north from west of this point. The increased flow during dropping tide north of the island was proportional to the strength of the SE wind.

Differences between wet season patterns and dry season tidal flow patterns were slight and related to: The estuarine basin being shallower (less volume) with less tidal range, and changes in offshore prevailing winds. In addition, most of the tidal water that moved into the bay returned (80-90%), but bay water salinity was much higher than during the rainy season.

In summary, the estuarine zone volume was less than during the wet season because of lower tidal cycles with the prevailing offshore winds. Not only was the basin volume less, but so was the tidal volume. Tidal range was approximately 30cm during the dry season in contrast to 45cm during the wet season. This was due to the limited influence offshore winds had on nearshore waters. Fetch was limited and the high fringing mangroves produced a wind shadow for a distance of 100 to 200M from shore. The northwest winds, however, produced a weak southerly littoral current, and the tide moved out of the basin into the shallow bay to the east and southeast of the study area.35 Figure 15. A. Water current patterns for rising wet season spring tide. Current arrow widths are relative to current strength, the wider the arrow the greater the water current. B

. Dry season36 falling spring tide. These current patterns were determined during numerous field days while depth and sediment profiling, soil coring, and canoeing across bay for access to coastal wetlands.

P. Estimated freshwater discharge required. The first step to calculate the volume of freshwater to be released was to determine the volume of water needed to reach the Bay. The combined effects of transpiration and evaporation minus marsh rainfall plus the loss of water from the Bay from evaporation minus rainfall over the Bay was determined. Two conditions were calculated, dry season and wet season spring tides:

V

water = [(T marsh x A marsh ) + (E marsh x A marsh ) – (R marsh x A marsh )] + [(E estuarinex A estuarine) – (R estuarinex A estuarine)], where

V = Volume T = Transpiration rate, A = Area, E = Evaporation, and R = Rainfall.

Tmarsh = 551,700M 2 x –5 L/M2 /d = -2,758.5 M 3 /d (for both dry and wet season).

Emarsh = 551,700M 2 x –5.5 L/M2 /d = -3,034.4 M 3 /d (dry season)

= 551,700M2 x –2.3 L/M2 /d = -1,268.9 M 3 /d (wet season)

Rmarsh = 551,700M 2 x 1.6 L/M2 /d = 886.7 M3 /d (dry season)

= 551,700M2 x 4.7 L/M2 /d = 2,593 M3 /d (wet season), therefore:

Eestuary = 65,500M 2 x -5.5 L/M2 /d = -360.3 M 3 /d (dry season)

= 81,700M2 x -2.3 L/M2 /d = -187.9 M 3 /d (wet season)

Restuary = 65,500 M2 x 1.6 L/M2 /d = 106.9 M 3 /d (dry season)

= 81,700M2 x 1.6 L/M2 /d = 130.7 M 3 /d (dry season) = 81,700 M2 x 4.7 L/M2 /d = 383.9 M 3 /d (wet season)37 Dry season Wet season Tm -2,758.5 -2,758.5 Em -3,034.4 -1,268.9 Rm 886.7 2,593.0

Ee -360.3 -187.9 Re 130.7 383.9

Vtotal (M 3 /d) = -5,135.8 -1,238.4

The volume required for any restoration water to make it to the Bay, because of ET losses, will decrease with time in the study area. In the beginning, water will be delivered as sheet flow, maximizing ET. However, over a period of time, delivered water should begin to channelize, and most water will reach the Bay via the creek channel minimizing loss due to ET. If additional water is discharged during the first few months of delivery, perhaps up to a year, the channelization process may take place more quickly.

Freshwater discharge volumes for different salinity targets, both the dry and rainy seasons, were calculated based upon flow charts ( Figure 9 ), and listed with other model parameters ( Table 2 ). The salinity model flow charts, using appropriate data from Table 2 , visually present the relationships between the different estuarine basin components. These components are needed to calculate freshwater discharge required to meet a target salinity. The first component is the total basin volume (Table 2.F.) and target salinity (Table 2.A.) at a state of quasi-equilibrium. Two components were derived from the total basin volume, the tidal volume and the retained estuarine volume, both at target salinities. The tidal volume component (Table 2.G.) was divided into one outgoing component, tidal volume lost, and two incoming components, Biscayne Bay replacement water and freshwater discharge. In order to maintain the target salinity, the combination of Biscayne replacement water and salinity (Table 2.B.) plus freshwater discharge must equal the water mass and salinity lost during each tidal cycle. Sea salt was considered a conservative parameter of seawater, which permitted straightforward mass balance equations. Data for dry and rainy season spring tides at different estimated tidal volume losses (10, 20 and 30% for dry season and 23, 33 and 43 % for rainy season) and various Bay salinities (21.5 and 30 for the dry season and 15.5 and 20.5 ppt for the rainy season) are presented ( Table 8 ). The midrange value for percent tidal loss is then predicted (Table 2.O.) and calculations were also made for plus and minus 10%. Mean Bay salinities for the season were used and a value that represented a typical high, but not extreme, salinity value.

On a typical dry season spring tide cycle, approximately 825M 3 of freshwater discharge is required to maintain a estuarine salinity of 15ppt. In contrast, a rainy season freshwater discharge of approximately 5372M 3 is required to maintain the target salinity of 7 ppt.38 The relationship between tidal loss and freshwater discharge volume at various Bay salinities were expressed for target salinity of 15 ppt for the dry season and 7 ppt for the rainy season ( Figure 16 ). The relationship between freshwater discharge and Bay salinity at various tidal volume losses were expressed for both the dry and wet seasons (Figure 17 ). These two figures also aided in illustrating the range of freshwater discharges required to cover small to medium changes in salinity of tidal volume. Tidal volume was much greater during the rainy season than the dry season with more tidal volume lost per tidal cycle because of the stronger northern longshore processes.39 Table 8. Summary data for calculation of freshwater discharge.

Ev Es Tv Ts Tv lost % lost Ts lost FWQ vol FWs Bv Bs Tv replaced Ts

dry 20445 15 14445 15 2889 20 15 1445 0 1445 21.5 2889 10.8 2889 20 15 963 0 1926 21.5 2889 14.3 2889 20 15 825 0 2064 21.5 2889 15.4 2889 20 15 722 0 2167 21.5 2889 16.1 4334 30 15 2167 0 2167 21.5 4334 10.8 4334 30 15 1445 0 2889 21.5 4334 14.3 4334 30 15 1239 0 3095 21.5 4334 15.4 4334 30 15 1083 0 3250 21.5 4334 16.1 1445 10 15 723 0 723 21.5 1445 10.8 1445 10 15 482 0 963 21.5 1445 14.3 1445 10 15 413 0 1032 21.5 1445 15.3 1445 10 15 361 0 1084 21.5 1445 16.1 1445 10 15 723 0 723 30 1445 15 2889 20 15 1445 0 1445 30 2889 15 4334 30 15 2167 0 2167 30 4334 15 wet 42525 7 29302 7 6739 23 7 3370 0 3370 15.5 6739 7.8 6739 23 7 3530 0 3209 15.5 6739 7.3 6739 23 7 3744 0 2995 15.5 6739 6.9 6739 23 7 4043 0 2696 15.5 6739 6.2 9670 33 7 4835 0 4835 15.5 9670 7.8 9670 33 7 5065 0 4605 15.5 9670 7.3 9670 33 7 5372 0 4298 15.5 9670 6.9 9670 33 7 5802 0 3868 15.5 9670 6.2 12600 43 7 6300 0 6300 15.5 12600 7.8 12600 43 7 6600 0 6000 15.5 12600 7.3 12600 43 7 7000 0 5600 15.5 12600 6.9 12600 43 7 7560 0 5040 15.5 12600 6.2 9670 33 7 6154 0 3516 20.5 9670 7.4 9670 33 7 6336 0 3334 20.5 9670 7.1 9670 33 7 6447 0 3223 20.5 9670 6.8 12600 43 7 8018 0 4582 20.5 12600 7.4 12600 43 7 8255 0 4345 20.5 12600 7.1 12600 43 7 8400 0 4200 20.5 12600 6.8 6739 23 7 4288 0 2451 20.5 6739 7.5 6739 23 7 4415 0 2324 20.5 6739 7.1 6739 23 7 4493 0 2246 20.5 6739 6.840 y = 41.3x - 0.3333 y = 72.2x + 1 y = 162.8x - 0.4 y = 192x - 0.6667

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

0 5 10 15 20 25 30 35 40 45 50
Tidal Volume Loss (%) 30ppt 21.5ppt 15.5ppt 20.5ppt W et Seaso n

Dry Season

Figure 16. Changes in salinity in relationship to freshwater discharge and tidal volume.

y = 36.471x - 371.12 y = 72.941x - 743.24

y = 109.18x - 1108.3 y = 134.2x + 1663.9 y = 192.8x + 2383.6 y = 251x + 3109. 5

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

0 5 10 15 20 25 30 35 Biscayne Bay Salinity (ppt)Freshwater Discharge (m3)

23% Tidal Loss

33% Tidal Loss
43% Tidal Loss

10% Tidal Loss
20% Tidal Loss

30% Tidal Loss Wet Season

Dr y Seaso n

Figure17

. Relationship between freshwater discharge and Biscayne Bay salinity.

Total freshwater discharge required . Total freshwater discharge required was calculated by two different methods. The first and simplest was to estimate water discharged through a channel with a known cross sectional area and flow velocity. This calculation produced the volume of water discharged and not necessarily the volume of41 water required to meet salinity targets. The paleochannel that delivered most of the water in the study area was 35cm deep and 5M wide. We assumed a flow velocity of 1 cm/sec. This was a very slow rate, which was the average flow rate at a nutrient dosing site in Shark River Slough. This must be a gross underestimate for use at this site because of the greater slope at the study site than in Shark Slough. The discharge based upon a flow rate of 1cm/sec was 0.618cfs (1.2 ac-ft/day), at 5cm/sec (6ac-ft/day) flow rate discharge was 3.1cfs and at 10cm/sec 6.2cfs (12 ac-ft/sec). This was even more of a conservative estimate than that based upon low flow rates, because more than one creek emptied into the study area, and during high flow periods considerable sheet flow adjacent to the channel certainly was present.

The second method was more complicated, and was directed at estimating the volume of water needed to produce the target salinity regime. The total volume of freshwater released was the product of the volume of water lost getting to the Bay plus evaporative losses from the estuarine surface and tidal loss replacement. The sums of these two products for both the dry and rainy seasons have been tabulated ( Table 9 ). These figures are to be considered a first approximation because of the difficulty of quantifying many of the model parameters. The system should be designed to deliver twice the discharge calculated in order to accompany new discharge values after monitoring and to handle more extreme climatic events.

Table 9

. Estimate for freshwater discharge required to meet salinity targets. Season Target salinity Bay salinity Marsh and surface estuary loss Tidal loss replacement volume (M 3 ) Total

(ppt) (ppt) (M 3 ) (Tide cycle) (Day) (M3 ) (ac-ft/d) Dry 15 21.5 5,135.8 825 1,650 6,786 5.5 30 1,445 2,890 8026 6.5 Rainy 7 15.5 1,238.4 5,372 10,744 11,982 9.7 20.5 6,336 12,672 13,910 11.342 RECOMMENDATIONS

.

1. Water is discharged until initial salinity target is reached. 2. Delivery mechanisms should be able to discharge twice the initial estimated freshwater volume. 3. Above delivery schedule is utilized while being monitored for two months. 4. After initial monitoring period, adjustment made to parameters. 5. Followed by another monitoring period to make final adjustment. 6. Addition adjustments may also be required, especially if extreme climatic conditions prevail. 7. As channelization occurs, readjustments will have to be made. 8. The relatively inexpensive addition of oyster shell subtidal bars would aid in retention of freshwater and provide good substrate for oyster community development. A few shallow barge loads of shell would suffice.43 REFERENCES CITED

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Wells, H.W. 1961. The fauna of oyster beds, with special reference to the salinity factor. Ecol. Monogr., 31(3): 239-66.

Yonge, C.M. 1960. Oysters. Willmer Brothers and Haram, Ltd., Birtenhead, London, England. 209p.Appendix 1. Core Descriptions.

GPS Core # Longitude Latitude Depth (cm) Description 8/7/01-1 25.49186 80.33849 0-27.5 35M south of east end of island. 0-12.5 Tan marine marl with Halodule roots. Sample A from 0-4cm Sample B from 8.5-12 cm 12.5 Erosional unconformity 12.5-27.5 Dark grey, black mottled freshwater marl with mangrove roots Sample C from 20.5-22.0 cm

8/7/01-2 25.49187 80.33844 0-28 1M north of 8/7/01-1 0-10 Recent organic muck with Halodule roots. 10-19 Marine marl with oysters Sample A from 13-15cm 19-28 Freshwater marl grading downward to dark black freshwater marl with mangrove roots and limestone clasts at base. Sample B from 23-25cm

8/7/01-3 25.49201 80.33829 0-10 Marine shell debris Sample A from 4-6cm 10-17.5 Marine marl with oysters Sample B from 13-15 cm 17.5-46 Freshwater marl with Cladium roots Sample C from 30-32cm

8/7/01-4 25.49215 80.33811 10 m s outh of east tip of island 0-10 Skeletal marine muck 10-18 Oysters Sample A from 13-15cm 18-26 Transitional marine to freshwater marl 26-61 Freshwater marl with Rhizophora rhizomes and Cladiumrootlets Sample B from 50-52cm

8/7/01-5 25.4926 80.33785 Same sequence as 8/7/01-451 Labeled: Outside Blowout #2

Depth (cm) Description 0-4 Yellowish grey silt. Large rhizomes. Buried Thalassiablades. 4-11 Brownish gray rooted silty mud. Root hairs and rootlets throughout. Rhizomes at bottom. 11-17.5 Grey silty mud. Fossil fragments slightly larger, some small mollusks. No cams. 17.5-26 Grey silty mud. Very small fossil fragments. No appreci able laminations. 26-29 Light brown grey silt. Small gastropods and fragments of echinoderm spines. Some black organic blobs, slight lamination. 29-40 Grey yellow shelly mud. Calcareous algae and shell fragments. Distinct lamination. 40-51 Grey brown mud. Few marine shells. Scattered black flecks, more toward top layer.

Labeled: long core (channel?)

1-10 Medium grey shelly mud. Numerous rootlets, Thalassia on top. Some large bivalves, most fragments, all look reworked. 10-13 Medium grey shelly mud. Some whole small gastropods. Most are fragments, mollusk bits. One large bivalve at top of sequence. 13-46 Long sequence of dark grey-brown mud. Probably carbonate. Many vertical black rootlets. Fine root hairs in places. At 16 cm is a round shrimp-like burrow filled with shell hash similar to layer above. At about 29cm the mud changes color gradually with more yellow below this Lower half also has red rhizomes 5mm and 10mm diameter. No obvious mollusks in this area 46-50 White carbonate mud -- looks like decayed ooilite. Few shell fragments

LTS 0-6 Grey brown rooted mar. Root hairs, roots, organic bits. Organic roots. May be in raint layers.

Core B Everglades 0-6.5 Black peat, large roots, elocharis at top. 6.5-13 Black peat, few fine roots.52 Core 8/11/00 -- 1 Creek channel at 10 1M mark. 60cm long. 0-2 Leaf litter. 2-7 Black peat with small roots. 7-17 Dark brown-black fibrous peat with small roots. 17-32 Red peat with large roots and root hairs 32-34 Grey brown black marly p eat with small roots 34-37 Grey peaty marl 37-43 Grey brown black marly peat with small roots 43-54 Grey brown black peaty marl 54-60 Grey brown marly peat with coarse sand to fine gravel size grains. Several pebbles <1cm

10-15 M inside mouth of creek

0-2 Dark brown mud (artifact) 2-5.5 Large limestone rock. 5.5-9 Grey rooted mud. 9-11 Mangrove peat 11-13 Grey rooted mud. Numerous small gastropods. 13-20 Light grey mud. Gastropods. Plancrsiscommon. Rooted. 20-21 Rootup layer 21-42 Light grey mottled mud. Roots (some large). More gastropods toward top. More bivalve fragments. 42-46 Dark peaty mud. Some "old" bivalve fragments and gastropods at base.

Creek Channel Core 3/20/01 0-8 Brownish grey carbonate mud with Haloduleroots and some shell fragments throughout 8-13 Shelly brown grey mud with bivalve fragments. Dominating the large fractions these are10-22mm. No ID on small fragments. Abundant. No orientation 13-51 Silty greenish grey dense carbonate mud. Large number of vertical roots more abundant at top. Shelly filled burrow approximately 2 cm diameter tube. Some mangrove roots. Scattered quartz silt (fine) in mud. Many small horizontal rootlets.

3/14/01 1/2 way between island and point in eel grass 0-11 Rooted grey mud, bivalves mostly fragments, mollusks decrease with distance to bottom. Several whole planorbis

. 11-15.5 Lighter grey mud, rooted. Shell fragments. Few sand size particles.

15m S off Turkey Point Transect, W of L-31E Levee53 0-3 Hydrobid rich brown peaty marl 3-6 Brown-grey mottled fibrous marl, many rootlets 6-13 Light grey carbonate mud, numerous root hairs 13-15 Grey carbonate mud. Few snails. 15-25 White carbonate mud with large plant roots. Sawgrass blades

9/12/01-1 0-4 Dark brown peat, marine shells, many roots 4-7 Dark brown peat and moderate grey peaty marl. Marine shells. 7-9 Dark brown marly peat, many root fibers. A large Gyraulus parvusshell. 9-16 Light grey and white marl. 16-18 Moderate brown peaty marl. Physella cubensis and small Gyraulus parvusshells.

1/2 way between 15 and 81m in eel grass (3/14/01-2) 0-2 Mat of Halodulestems in moderate brown peaty marl 2-7 Brownish-grey marl with C ladiumleaves 7-16 Moderate brown peaty marl. Many shells and several Biomphalaria havanensis shells more Halodulestems.

9/12/01-2 0-8 Dark grey marl with many fine roots. Either Littoridinops monroenisor Aphaostracon pachynotusshells

9/12/01-3 0-3 Moderate brown peaty marine sediment. Haloduleleaves. 3-18 Dark brown peat many roots, some round dark stems/roots.

9/12/01-4 0-11 Small amount of dark brown peat, mostly mangrove debris, leaves, propagules, and roots 11-34 Dark brown fibrous peat, many fine root hairs, some large woody plant debris.

9/12/01-5 May be re versed 0-19 Moderate grey marl, many woody roots, Thalassialeaves on top. 19-43 Very shelly light grey marl, Thalassiaembedded throughout 43-55 Moderate grey marl, Haloduleon surface, moderate amount of shells

Oyster Core 1 0-14 Moderate brown peat, many roots and rootlets. Many plant parts, oysters between 12-1454 14-21 Very shelly moderate brown peat, still many brown plant parts (very round outside coverings of some kind of plants) 21-40 Moderate brown peaty marl. Moderate amount of shells. Still brown fibrous material. 40-65 Moderate grey marl. Several Gyraulus parrusshells many fibrous roots. Still cylindrical plant material 65-72 Dark brown peat with fibrous roots, large particles of limestone.

Labled A-N 0-15 Very fibrous dark brown peat. Many large stems and various sizes of roots. 15-56 Very dark brown peat. Very fibrous. Roots are smaller than layer above. 56-75 Moderate brown peat. Root sizes consistent with layer above. More shell fragments.

10m N of E end of island (also oyster core 3) 0-18 Very shelly marine marl, dark grey, oysters at bottom of layer. 18-29 Light grey brown marl. Thick woody roots 29-31 Dark brown peat, fibrous and shelly. 31-33 Light grey brown marl. 33-47 Dark brown peaty marl very shelly. Some Sphaostracon pachynotusshells. Large limestone particles.

9/12/01-6 Dr. Jaff ee core? 0-10 Light brown marl mottled with dark brown peat. Many marine shells. Oysters at bottom of layer 10-12 Very fibrous dark brown peat 12-41 Light brownish grey m arl. Several Gyraulus parvus 41-42 Dark brown peat, very fibrous. 42-53 Dark grey marl, several large limestone clasts.

Oyster Core 1 0-2 Light grey marine sediments. Oyster shells. 2-23 Dark brown peat, very fibrous, many large roots (sawgrass?) Oysters at top 26-57 Light brownish grey marl. Very fibrous and many large roots. Gyraulus parvus 57-82 Dark grey peaty marl. Many large roots or stems. 82-89 Very dark brown peat. Some shells.

9/12/01-7 0-17 Very shelly marine deposits. Dark grey marl. 17-58 Grey green marl with pockets of shells scattered within. Long vertical Cladium roots. Small limestone clasts at bottom.55 10m Offshore N end of Island 0-12 Very shelly light grey marine marl. 12-30 Very dark brown peat, sawgrass roots 30-50 Very dark brown peat, many shells including Biomphalaria havanensis and Physella cubensis

9/12/01-8 0-5 Plant stems 5-21 Moderate brown very fibrous peat 21-61 Very dark brown peat, few roots. Limestone clasts at bottom.

Levy Transect 0-18 Dark brown fibrous peat. Large mangrove stem, leaf litter, root material. 18-33 Dark brown fibrous peat. Much big plant material. Fleshy stems. 33-55 Dark brown fibrous peat. Less big plant material 55-62 Peaty marl with many shell fragments.

9/12/01-9 Core that Pete worked up 0-81 Very dark brown fibrous peat. Many roots and fleshy plant stems. 81-99 White marl, large amount of fibrous root material.