Impacts of Hydrological Restoration on Three Estuarine Communities of the Southwest Florida Coast and on Associated Fauna

Project Proposal for 2001

USGS Biological Resources Division

IDENTIFYING INFORMATION

Project title: Impacts of hydrological restoration on three estuarine communities of the Southwest Florida coast and on associated fauna
Geographic area: Southwest Florida
Project start date: October 1, 1999
Project end date: September 30, 2004

Project chief: Carole C. McIvor (Ecology Coordinator)
Region/Division/Team/Section: CCM - ER/BRD/FCSC/REB
Email: carole_mcivor@usgs.gov
Phone: (727) 803-8747
Fax: (727) 803-2032
Mail address: Center for Coastal Geology & Regional Marine Studies, 600 Fourth Street South, St Petersburg, FL 33701
Program(s): Place-based science

NARRATIVES
Project Summary: A primary goal of Everglades restoration is the recreation of water flows and water quality more closely approximating pre-drainage conditions in both freshwater and estuarine ecosystems within Everglades National Park. These estuarine systems include submerged aquatic vegetation, mangroves (tidal forests), and brackish marshes. Three primary groups of animals are closely associated with, and often dependent upon, one or more of these ecosystems: fish and decapod crustaceans (shrimp, crabs), manatees, and wading birds. Herein we focus on fish and decapod crustaceans, and manatees. (Wading birds will be addressed in future efforts.) The present proposal addresses how hydrological changes upstream are likely to affect: (1) the distribution, abundance and composition of submerged aquatic vegetation and selected animal inhabitants; and (2) the distribution and abundance of selected biota associated with mangroves and brackish marshes.

Submerged aquatic vegetation (SAV) is an integral part of many shallow-water estuarine and coastal systems worldwide. Such vegetation (generally termed seagrass when it occurs in near-marine salinities) provides many benefits to society including sediment stabilization, habitat for estuarine animals including manatees, and direct and indirect support of commercial and recreational fisheries. Very little is known of the submerged aquatic vegetation of the southwest coast of Florida and the associated rivers draining the Ten Thousand Islands where riverine water flows are projected to change as a result of Everglades Restoration. Importantly, the species composition and standing stocks of SAV (and macroalgae) appear to be quite sensitive to salinity variation such as that caused by seasonal and anthropogenic changes to freshwater inflow.

West Indian manatees are endangered aquatic mammals that inhabit the coastal rivers, canals, and estuaries on both coasts of South Florida year-round. Because manatees are reliant on submerged aquatic vegetation for feeding, we expect that manatee distribution, relative abundance, habitat use, and movement patterns will change as a result of altered water management regimes and resulting changes in nearshore salinity. This problem will be addressed through (1) the development of a spatially-explicit, individual-based model that will predict manatee response to different restoration scenarios, and (2) comprehensive field studies in southwest Florida that will provide data for the model and that will document the current distribution and status of the manatee population prior to implementation of restoration activities.

Concern about the fate of mangrove ecosystems derives from their known use as habitat for a wide range of both terrestrial and aquatic animal species, especially fishes and decapod crustaceans of forage as well as of commercial and recreational importance. Additionally, mangroves at the mangrove/marsh boundary in southwestern Everglades National Park were historically the sites of extensive colonial wading bird nesting areas. Birds apparently foraged and fed their young primarily from adjacent brackish marshes. One of the goals of Everglades Restoration is return of extensive wading bird rookeries to these headwater mangroves. It is therefore essential that we understand the dynamics of fish (and decapod crustaceans) in mangrove and adjacent marsh habitats in order to judge the effectiveness of restoration of the forage base necessary to support wading bird rookeries. Manatee use of open estuarine waters may also change in response to changes in freshwater delivery patterns.

The objectives of this proposal are thus to:

• quantify the range of physical factors that influence SAV distribution and development;
• describe the SAV of representative tidal rivers and nearshore coastal waters;
• quantify the dynamics (spatial and temporal patterns of the density and biomass) of small-sized fishes and decapod crustaceans in intertidal mangrove forests, brackish marshes, and SAV and to relate these distributional patterns to hydrological and environmental factors;
• determine the relative abundance of large fishes in flooded mangrove forests along the complex environmental gradient present in Shark/Harney River;
• determine the distribution, relative abundance, movement patterns, home range, and population parameters of manatees in southwestern Florida;
• in association with ATLSS modelers, predict how the type and distribution of SAV is expected to change with hydrological restoration of the Everglades;
• in association with ATLSS modelers, build and test a model of manatee response to hydrological restoration.

Background: There are at least two reasons why it is imperative to understand the dynamics of SAV in the nearshore coastal area and in tidal rivers and bays of the SW Florida coast. Firstly, the species composition and standing stock of SAV (and macroalgae) appear to be quite sensitive to salinity variation such as that caused by seasonal and anthropogenic changes to freshwater inflow (Tabb and Manning 1962; Flores-Verdugo et al. 1988; Montague and Ley 1993; Carruthers et al. 1999). Secondly, hydrological restoration in the freshwater portion of the Greater Everglades Ecosystem will modify freshwater delivery patterns to the southwest rivers and shallow nearshore waters.

Submerged aquatic vegetation (SAV) is a common ecosystem component in freshwater, estuarine and marine environments where light penetrates the water column, bottom sediments are adequate for plant growth and water velocity is not excessive. The functional roles of SAV in ecosystems include sediment stabilization, nutrient cycling, primary production, and habitat or foraging grounds for a wide variety of animals including invertebrates (e.g., Cyr and Downing 1988), fish (e.g., Chick and McIvor 1994), manatees (e.g., Thayer et al. 1984), turtles, and wading birds (Powell et al. 1989a). Compared to unvegetated sediments, submerged aquatic vegetation supports higher numbers of invertebrates (Crowder and Cooper 1982), fish (Rozas and Odum 1987), and commercially important crustaceans such as blue crabs (Orth and Montfrans 1987). In the estuarine portions of Everglades National Park, SAV and mangroves constitute the two most frequently used nursery areas for estuarine transient fish and decapod crustacean species, i.e., those that reproduce offshore and whose juvenile stages rear in estuarine waters (e.g. Zieman 1982; Odum et al. 1982). Additionally, areas of tidal rivers with SAV are important winter-feeding and resting areas for manatees, a threatened species (Snow 1991; 1992). Manatees also utilize nearshore grass beds on the southwest coast, primarily during the summer months (S. Snow, ENP, pers. comm.). However, there are no systematic surveys of SAV along the nearshore SW coast, or in any of the tidal rivers and inner bays.

The first qualitative description of the SAV of the southwest Florida coast is that of Reimann (1940) who described SAV so abundant that it repeatedly fouled the boat propeller in Shark River upstream of Tarpon Bay. However, this area appears depauperate in SAV at present. Tabb and Manning (1962) described the SAV of Coot and Whitewater Bays, and Montague and Ley (1993) did the same for Taylor River, Snook Creek and Highway Creek, tributaries of NE and northcentral Florida Bay. Briefly, all these locations were dominated by some combination of the angiosperms Ruppia maritima and Halodule wrightii, and the macroalgae Chara hornemanii and Batophora. Both groups of investigators reported considerable spatial and temporal variation in SAV of these oligohaline to mesohaline sites. Montague and Ley (1993) linked the low standing stocks and extreme temporal variability in SAV of oligohaline upstream reaches to salinity variability, in part due to delivery from the C-111 canal. It is likely that the communities of SAV in the tidal rivers and bays of the southwest coast also show considerable temporal variability.

In South and SW Florida, seagrass beds in Florida Bay are by far the best-studied communities of submerged aquatic vegetation. Much is known of these beds as a result of their large spatial extent (1,660 km²), recent die-off problems, and their contribution to both the regional ecosystem and to the human community (e.g., Bull Mar Sci., Vol. 44(1) 1-526 and Vol 54(3) 577-1094). Far less well known are the communities of SAV that occur in two other geomorphic settings in SW Florida: in tidal rivers that deliver freshwater to the Gulf; and in the relatively turbid nearshore coastal waters (Dawes et al. 1995).

The geomorphology of the southwest rivers (Shark/Harney, Broad, Lostmans) is distinctive in that they are marked by one or more interior bays (Figure 1). These interior bays, in turn, are often connected between adjacent rivers by small channels. These river systems are uniformly shallow (< 3 m) and the bays even more so (< 2 m) (Nautical Charts 11430, 11429). Water clarity is frequently quite good (pers obs). Whereas the riverine channels are largely scoured to bedrock (R. Halley, USGS, GD, pers. observations), the broad, shallow bays contain adequate sediment to support SAV. Nonetheless, virtually nothing is known of the submerged aquatic vegetation in these tidal rivers.

There is a large body of literature on environmental factors that influence the development and productivity of SAV in a variety of habitat types. Briefly, sediment depth and composition (grain size, organic content, nutrients); water column characteristics including light penetration, nutrient and salt content; physical disturbance (as from storms); and grazing by herbivorous animals are probably the major influences (e.g., Zieman 1987; Powell et al. 1989b; Valentine and Heck 1999).

Manatees inhabit the coastal zone, rivers, and canals of South Florida from the St. Lucie estuary on the Atlantic coast to Charlotte Harbor on the Gulf coast, and inland to Lake Okeechobee (Lefebvre et al. 1989). Restoration of semi-natural patterns and timing of freshwater flows through the Everglades is expected to result in decreased freshwater inputs to Biscayne Bay, increased inputs to Florida Bay, and redistribution of surface water flow to simulate the historical sheetflow pattern in the Big Cypress - Ten Thousand Islands region. Major changes in the distribution of freshwater sources and submerged aquatic vegetation may substantially alter the suitability of these habitats for manatees, which are apparently closely tied to freshwater by physiological requirements, and to SAV for foraging requirements. One specific hydrological restoration project that will be initiated soon (year 2001, T. Hopkins, Rookery Bay NERR, pers. comm.) is the Southern Golden Gate Estates development, which is drained by the Faka Union Canal system. Large numbers of manatees (up to 200-300, S. Snow, ENP, pers. comm.) aggregate at the Port of the Islands basin in the upper Faka Union Canal during winter cold periods, and the canal is also frequented by manatees during the warm season. They are apparently attracted by warmer temperatures associated with the deeper waters (and perhaps artesian springs) of this dredged canal and by the ready source of freshwater. Implementation of the hydrologic restoration plan for the Southern Golden Gate Estates is predicted to reduce freshwater point flow discharges in this canal by two orders of magnitude and to minimize the freshwater shock loads to the Ten Thousand Islands Estuary (Abbott and Nath 1996). We can use this project as a large-scale experiment to assess the impacts of changes in freshwater inflow on manatee distribution, relative abundance, and habitat use in the Ten Thousand Islands region.

Just as SAV characterizes the nearshore shallows and inner bays of the southwest rivers, mangroves characterize much of the intertidal zone here. Mangroves actually exist along the southwest Florida coast in a variety of hydrological and geomorphological settings, but two are particularly common: fringing mangroves adjacent to predictably tidal rivers and bays (low in the intertidal zone and generally dominated by the red mangrove, Rhizophora mangle); high intertidal mangroves (often some distance from flowing water, and generally of mixed species composition) (Odum et al., 1982). Mangroves also grade into brackish marshes between adjacent tidal rivers, and in the headwater regions of rivers (Craighead, 1971; Tabb et al. 1974). We know a considerable amount about the factors affecting the organization, distribution, and productivity of the mangrove plant community (e.g., Odum et al. 1982; Smith 1992 and ongoing studies). However, we know far less about the factors affecting the fish and decapod crustacean communities associated with mangroves, particularly those of Florida's southwest coast.

There have been considerable advances in the last decade in the development of methodology for quantitatively sampling small fishes in densely vegetated habitats (reviewed in Rozas and Minello 1997). Additionally, there has been progress in linking patterns of abundance and composition of mangrove and marsh fishes with the physicochemical, flooding, geomorphological and structural parameters in specific locations (Thayer et al. 1987; Sheridan 1992; McIvor and Rozas 1996; Ley et al. 1999; Lorenz 1999). Despite this progress, there remain considerable gaps in our basic knowledge of the controls of secondary productivity, and of the distribution of marsh and mangrove fishes at the landscape level. The present proposal seeks to provide basic information relevant to understanding the spatial and temporal variation in fish assemblages for representative mangrove and brackish marsh habitats along the complex environmental gradients present along the Shark/Harney River system. Shark River is the primary (though not only) mangrove estuary likely to be influenced by hydrological restoration in the Greater Everglades Ecosystem.

The research described herein seeks to document the broad scale temporal and spatial patterns of SAV in nearshore coastal areas and in enclosed bays in selected rivers in the Ten Thousand Islands, to describe the species composition and peak standing stocks in these locations along salinity gradients from up- to downstream, and determine the suite of environmental factors that likely influence the development of submerged aquatic vegetation. Further, this research seeks to quantify the fishery community closely associated with beds of SAV, and relate manatee aggregations to SAV and salinity regimes. A major effort to construct an individual-based model of manatee population dynamics will be initiated in year two with existing data. This model will be extended, upgraded, and tested in future years based on heightened field efforts to fill data gaps in this particular geographic region. The proposed research initiative will be the first major effort to place manatee biology firmly in an ecosystem context. This will lead to improved understanding of both manatees and the aquatic vegetation upon which they depend, and is likely to generate further testable hypotheses about the role of manatees in the estuarine ecosystem.

Additionally, in future years, the study of SAV may be extended to the northern Ten Thousand Islands, and may take on additional components; an offshore mapping component (USGS NWRC mapping group) to extend from the Caloosahatchee River to Cape Sable; a bathymetric and sediment deposition component within the southwest rivers with GD; and an expanded collaboration with WRD to couple discharge and salinity measurements in the southwest rivers with SAV distribution.

OVERALL SCIENTIFIC QUESTIONS:

For the SAV portion of this proposal, the research described herein asks several questions for shallow nearshore areas and estuarine bays within representative southwest rivers including: (1) What are the spatial and temporal patterns of distribution and abundance of submerged aquatic vegetation? (2) How important is freshwater inflow compared to other environmental variables in controlling the extent of SAV? (3) How do fish and crustacean assemblages closely associated with beds of SAV vary along the salinity gradient and between rivers and seasons? (4) How closely are manatee distribution patterns linked to SAV? (5) Can we build a manatee model that incorporates known population and behavioral characteristics and predicts the response of this endangered mammal to the modified flows and salinity regimes that will result from Everglades Restoration? Beginning in outyears: (5) What roles do sediment transport and deposition play in SAV distribution and abundance? (6) Are the existing areas occupied by SAV likely to be modified by increased flows with restoration? (7) What are the nearshore and offshore limits of seagrass growth on Florida's SW coast?

For the mangrove and brackish portion of this proposal, the research described herein asks several questions for three emergent wetland types (fringing mangroves, high intertidal mangroves, brackish marshes) including: (1) Is mean annual primary productivity of the dominant wetland vegetation a good predictor of the average annual standing stock of fishes and crustaceans? (2) In terms of nutrient regime characteristic of a given wetland type, does fish and crustacean density (or standing crop) seem to be more closely tied to nutrient levels in sediments or water column? (3) What are the relationships between frequency and duration of tidal flooding, freshwater inflow (as reflected by salinity), hydroperiod (where appropriate), structural type and complexity of wetland vegetation, and secondary productivity of fish and crustaceans (as inferred from standing stocks)? (4) How do the seasonal and annual densities of fishes and crustaceans most frequently consumed by colonial wading birds vary across the various wetland types?

SPECIFIC PROJECT OBJECTIVES AND STRATEGY:

Project Objectives and Strategy. The ultimate objectives of the proposed research are to predict and assess how altered hydrologic regimes planned by restoration managers are likely to impact submerged aquatic vegetation, fish, decapod crustaceans, and West Indian manatees in a range of estuarine habitats in SW Florida. This five-year study takes a three-pronged approach to addressing this problem: synthesis of existing data, field studies to fill data gaps, and model development. Specific tasks are as follows.

Task 1: Convene a workshop during the first year to comprehensively assess the information available on manatees in South Florida. The effort will result in a data directory, which will list the available relevant databases, including geographic scope and years of study, on manatee distribution, relative abundance, movements, habitat use, mortality, and key habitat variables. An important aim would be to identify and prioritize gaps in our knowledge and to formulate specific studies to address them. The specific nature of the field studies on manatees proposed below would be guided by the results of this workshop.

Task 2: Determine the broad-scale patterns of temporal and spatial distribution and relative abundance of submerged aquatic vegetation in nearshore coastal areas and in bays of representative southwest coastal rivers. We anticipate focusing on three river systems initially. These are (from south to north): Shark/Harney River, Broad River, and Lostmans River (Figure 1). The sites to be targeted within each river system are as follows: in Shark/Harney River - Rookery Branch upstream, Tarpon Bay midstream, Oyster Bay downstream, and Ponce De Leon Bay nearshore; in Broad River - Lonesome Mound Bay upstream, Broad River Bay midstream, the mouth of Broad River downstream, and the unnamed shallow banks nearshore; in Lostmans River - Rocky Creek Bay upstream, Onion Bay midstream, First Bay downstream, and the unnamed shallow banks nearshore. This objective will be accomplished through a combination of a compilation of unpublished and gray literature sources, photo-interpretation of color low-level aerial photography, ground-truthing using the Braun-Blanquet cover method, and standard core sampling. Aerial surveys and ground assessments will be used to characterize important manatee habitat (Lefebvre et al. 2000).

Task 3: Determine peak standing crops of SAV and relate to environmental parameters. This objective will be accomplished by quantitatively sampling peak biomass during the summer wet season and again during the winter dry seasons along stratified random transects using standard techniques (e.g., Downing and Anderson 1985). We will use a variety of multivariate statistical techniques to integrate biological and physicochemical data (surface water discharge, groundwater discharge, sediment and water column nutrients, water clarity and depth, substrate characteristics). Sight selection will depend in part on known locations of manatee aggregations (Snow 1991, 1992).

Task 4: Conduct comprehensive field studies in southwest Florida to provide the baseline information necessary for documentation of the effects of hydrological restoration on the manatee population. Collect data on distribution, relative abundance, movement patterns, home range, and population parameters using aerial surveys, satellite-based radio-telemetry, and photo-identification of scarred individuals. These studies will provide the data necessary to evaluate model assumptions and to verify model outputs. The study area for the field studies will focus on the coastal rivers, bays, and estuaries of the southwest coast from Flamingo to Marco Island, including Everglades National Park and the Ten Thousand Islands. Although aerial surveys have been conducted in this area by FMRI and ENP biologists, this still remains the last geographic region where Florida manatee population biology and ecology have not been studied intensively.

The field effort will comprise the following standard data collection approaches: (a) Aerial distribution surveys provide data on the distribution and relative abundance of manatees over a wide area, as well as minimum counts (with no variance estimates) within the study area (Ackerman 1995, Lefebvre et al. 1995). They are valuable for examining seasonal and inter-annual trends in distribution and relative abundance, and for relating manatee spatial patterns to habitat variables. These surveys would be carried out twice monthly year-round in the coastal and backbay waters of southwest Everglades National Park and the Ten Thousand Islands; (b) We propose a feasibility study to estimate population size (with variance estimates) within the study region using standard aerial strip-transect methodology (Miller et al. 1998). We estimate that approximately 6 to 10 surveys would need to be flown over a short period during the warm season in the third and fifth years of the study. Continued repetition of such surveys in later years would provide a database over which temporal trends in abundance could be detected; (c) Argos satellite-based radio-telemetry will be used to provide information on the movements, home range, and habitat use of individual manatees using methods that have been successfully applied throughout the manatee's range (Rathbun et al. 1990, Reid et al. 1995, Deutsch et al. 1998). Up to 20 manatees will be tagged each year for a period of three years. They will be tracked in the field by boat and air and retagged at about six-month intervals; (d) Photo-identification of permanently scarred individuals has been used to document gross movements and reproductive histories of individuals over long periods of time (Reid et al. 1991, Beck and Reid 1995, Rathbun et al. 1995) and to estimate survival rates through application of mark-recapture analytical techniques (Langtimm et al. 1998). The lack of major warm-water springs or industrial effluents that lure manatees in winter, combined with the dark, tannin-stained waters of the region, make individual photo-identification a challenging task. Therefore, we propose a feasibility study, in cooperation with the Florida Marine Research Institute, to attempt shore- or boat-based photography at reliable manatee aggregation sites, such as the Port of the Islands basin on the Faka Union canal.

These four field approaches are complementary, each providing a different window on manatee biology. Approaches (a), (c), and (d) will first be applied to the Faka Union Canal and Bay region, if the State implements plans to purchase and restore the Southern Golden Gate Estates.

Task 5: Determine the species composition, density and biomass of fish and decapod crustaceans in SAV. This objective will be accomplished using well-established enclosure-trap methods (Rozas and Minello 1997), either the meter-square throw-trap method of Robblee et al. (1991) or a pop-net method (Morgan et al. 1988; Serafy et al. 1988), dependent on SAV density coupled with information gleaned from pilot studies. We envision taking at least 5 random samples/bay 3-4 times/yr depending on what we learn of the seasonal dynamics of the plants themselves.

Task 6: Define the spatial and temporal patterns of the density and biomass fishes and crustaceans in intertidal mangrove and brackish marsh habitats, and the hydrological and environmental factors associated with these patterns. Data on mangrove-associated fishes from Taylor Slough and northeastern Florida Bay demonstrate that depth of flooding, duration of flooding, mean salinity and salinity variation at a site significantly affect the species composition and relative abundances of fishes (Ley et al. 1999; Lorenz 1999). However, the results of research in this basin, particularly estimates of standing stocks, are not directly transferable to mangrove sites along the rivers of the southwest coast of Everglades National Park because of fundamental differences between the two regions. The estuarine zone of Taylor Slough is best considered nontidal or seasonally tidal, the sediments are nutrient-poor carbonate marls, and the mangroves are small in stature (1.5-2 m) and are characterized as dwarf type (Lugo and Snedaker 1974). In contrast, the estuarine zone of Shark River Slough has a predictable ca 0.75 m semi-diurnal tide, peat sediments underlie the mangrove forests, and the trees in fringing forests reach 15-20 m heights. One would predict that the combination of regular tidal flooding, nutrient subsidy provided by the tides, and richer peat substrates would result in higher standing stocks of fishes and crustaceans in mangrove habitats along Shark Slough compared to Taylor Slough.

This objective will be accomplished for small-sized organisms by use of either 6-9 m2 pull-up nets (Rozas 1992) or encircling "stake" nets (Vance et al., 1996; Ronnback et al. 1999) depending on the results of a pilot study of representative fish densities. Net locations will be fixed within the forest plots to avoid excessive mangrove trimming and disturbance: statistical analysis will properly reflect this fact. Replicate samples will be taken bimonthly, the schedule being determined in part by the necessity of adequately covering the important dispersal events of the wet season (and autumn sea-level rise), and the drawdown period of winter that results in concentration of fish and crustaceans in high marsh pools (Tabb et al. 1974). Animal data will be analyzed with repeated measures MANOVA. Principal components analysis and multiple regression analysis will be used to assess the effect of physical factors on metrics of animal abundance. Additional population-level information will be available from fish and crustacean samples. This information (e.g., timing and incidence of young life-history stages, size distributions of fishes and crustaceans known to appear in regurgitant samples from wading birds) will be used in developing the database essential to ATLSS modelers.

Larger-sized fishes will be sampled by use of trap nets with a cod end positioned at the mouth of intertidal rivulets (or gutters) that drain the mangrove forest (Robertson and Duke 1990). Large fish entering the flooded forest will be sampled at 2 intertidal rivulets per plot (S1, S2, S3, S4), the same general locations as for small fishes. Samples will be taken bimonthly. Nets will be set at slack high tide and retrieved near slack low tide. Mesh size will be larger (_ inch) than for nets that target small fish. The experimental design is a one-way analysis of covariance with the factor being position along the upstream to downstream gradient, and the covariate being estimated flooded area drained by a given net. Separate analyses will be run for dependent variables of relative abundance and biomass.

Task 7: Develop a spatially explicit, individual-based ecological model that can project the response of manatees—in terms of distribution, movements, and habitat use—to various hydrological restoration scenarios. The manatee model will be integrated into the ATLSS Everglades biotic modeling system and will be coupled with available models of hydrology and aquatic macrophytes. Existing data from South Florida and other better-studied regions of the state will initially be used to parameterize the manatee model. Additional field support studies (Task 4) will fill in data gaps as needed and allow refinement of the model structure and parameters for this region.

Because there is considerable year-to-year variability in freshwater discharge due to cycles of wet and dry, it will be necessary to continue this research for a period of at least 5 years to capture some of this variability. We expect after 5 years to be able to describe with considerable confidence the major patterns of temporal and spatial variation in all the parameters targeted above. Further we expect to be able to relate these patterns in SAV distribution, and of fish and crustacean distribution in all three communities (SAV, mangroves, brackish marshes) to a set of environmental variables of which we predict that salinity, salinity variability, and nutrient status of the sediments will be particularly important. This body of information will form the baseline for understanding the dynamics of the major plant and associated aquatic animal communities of the SW coastal region of Florida. The manatee model will prove invaluable to managers attempting to maximize water flows for the benefit of endangered species. Finally, much of the knowledge we gain will be crucial to extending ATLSS and ELM models into the mangrove transition zone of the SW coast where the effects of hydrologic restoration are expected to be most dramatic.

Potential impacts and major products: The manatee model will be a major product, and another tool with which to judge the effectiveness of specific restoration scenarios. For the remainder of the research outlined herein, it is important to note that in the present conceptual restoration plan, both the conceptual model and performance measures for the mangrove transition zone (USACOE 1999a,b) are restricted to a totally different dwarf scrub community on the northern shore of central and northeastern Florida Bay. At present, there are no conceptual model or performance parameters for mangroves and associated brackish marshes of the SW coast. Similarly, both the conceptual model and performance measures for submerged aquatic vegetation (USACOE 1999a,b) are restricted to a totally different vegetated community (dominated by Thalassia) in Florida Bay. Thus, the data collected in this proposed study will form the basis for: (1) developing conceptual models of the likely effects of hydrological restoration and modified salinity regimes on tidal mangroves, adjacent brackish marshes and SAV, and of and their fish and crustacean assemblages; and (2) developing performance measures for these communities. Additionally, this research will allow: (a) testing of the hypothesis of lowered estuarine productivity due to reduced freshwater inflow (Walters et al. 1992; McIvor et al. 1994); (b) testing of the estuarine compression hypothesis, i.e., that the oligohaline zone of the estuary has been compressed by decreased freshwater flow (Bjork and Powell 1993).

Collaborators, clients: Importantly, the experimental design of the mangrove and brackish marsh portion of the study is such that fish data collected in this effort will be maximally useful to both managers and to other research scientists and modelers in the arena of South Florida restoration. Specifically, we will sample at existing GCC (Global Climate Change) instrumented locations on Shark River (S1-S5) (see Figure 1) where data on both surface and groundwater depth and salinity are continuously recorded, where plant community structure and primary productivity of mangroves are known, and where surface water chemistry is routinely monitored. Additionally, we will sample temporally such that our data will be readily comparable to that of fish ecologists working in the freshwater Everglades. Personnel from ENP (Skip Snow) and FWS (Terry Doyle) will be involved in planning and conducting distribution and trend assessment aerial surveys. Finally, we will work closely with the ATLSS modeling team to provide data critical to building a manatee model, and to parameterize a mangrove transitional-zone model that includes higher trophic levels.

Similarly, the SAV studies described herein capitalize on the presence of hydrological monitoring sites in Shark and Lostmans Rivers (funding to T.J. Smith under the USGS/BRD's Global Climate Change program) and the discharge stations of WRD on Shark, Broad and Lostman's Rivers (Levesque 1996). Our studies will also rely on other water quality data collected in these rivers under either ENP, or the Southeast Environmental Research Center (SERC) at FIU. Additionally, the SAV data collected herein will be directly comparable to two other sets of SAV data collected in an analogous manner under the auspices of some combination of funding from USGS/BRD, NPS, and the South Florida Water Management District. Specifically, Fourqurean and Richards are estimating SAV standing stocks for sites in Cuthbert and West Lakes in southcentral ENP, and Robblee and colleagues are conducting similar research on seagrasses in Florida Bay. The data on fishes and crustaceans will likewise be directly comparable to analogous data being collected in the freshwater Everglades marshes (Loftus et al. 1997), intertidal mangroves and brackish marshes of Shark River (McIvor and Smith CESI proposal), and seagrass beds of Florida Bay (Robblee and colleagues).

The proposed manatee research dovetails nicely with manatee research efforts and management priorities for species recovery. Firstly, formulation of an individual-based model should prove useful to address urgent management issues throughout the manatee's range. In particular, managers need predictions of manatee response to the interruption of warm-water discharges from industrial facilities - a problem that could be evaluated with the type of model developed in this study. This is a subject of great concern given the proposed deregulation of the electric utility industry in Florida. Secondly, the Florida Manatee Recovery Team has placed a high priority on obtaining estimates of population parameters in southwest Florida, given that up to one-third of the manatees statewide could be in this region. The quantitative criteria for downlisting proposed by the Manatee Population Status Working Group and currently under serious consideration by the Recovery Team require estimates of population growth rate for several regions in the manatee's range. Radio-telemetry will help determine the degree of interchange of manatees with adjacent regions to the north and in southeast Florida. A powerful approach for estimating growth rate is through demographic modeling of stage-specific survival and reproductive rates (Eberhardt and O'Shea 1995). Long-term demographic data are available for the east and northwest coasts of Florida, but they are not yet available for the southwest region of the state. Researchers at the Florida Marine Research Institute (FMRI) are collecting the necessary photo-identification data in Tampa Bay and Ft. Myers, and we propose to coordinate with them to provide additional data south of Naples. If successful, this will fill in a major geographic gap in our understanding of manatee population biology.

Lastly, captive-born and captive-reared manatees that are naive about the natural environment have been released in the southwest Everglades in recent years. The lack of human development, along with the relatively warm winters, were among the primary reasons favoring this region. While preliminary results are promising, our lack of information on the movement patterns of wild manatees in the region has hindered evaluation of the success of these reintroduction efforts. A concentrated field effort here will resolve this problem.

While the exact roles of the agencies and individuals remains to be determined, it would be logical for the ENP to continue to be involved with manatee aerial surveys and field tracking, and for FMRI to be involved with photo-identification, assistance with field tracking north of the study area, and aerial surveys. In addition, FMRI might contribute to development of spatially referenced databases of environmental variables and to parameterization of the individual-based model using radio-telemetry data from the west coast. We expect to work with the veterinarians and husbandry staff of Sea World of Florida and Miami Seaquarium to assist with manatee captures.

Numerous clients will be interested in the output from this project. These include: the National Park Service, U.S. Army Corps of Engineers, the Federal Taskforce for South Florida Restoration, U.S. Fish & Wildlife Service, National Oceanic and Atmospheric Administration, Natural Resources Conservation Service, Rookery Bay National Estuarine Research Reserve, Big Cypress National Preserve, Florida Fish and Wildlife Conservation Commission, Florida Department of Environmental Protection and counties in South Florida (including Collier, Monroe, and Dade). Study findings summarized in our final report will provide the Federal Taskforce for South Florida Restoration with additional scientific information for restoration planning and evaluation. Insight provided by our research on submerged aquatic vegetation and its associated biotic community will benefit the general public, environmentalists, scientists, tourists, farmers, and commercial businesses that are concerned with, and affected by, Everglades restoration.

PROJECT SCHEDULE AND PRODUCTS: This schedule reflects delays incurred during year 1. An additional three years will be necessary to complete the project.

DELIVERABLES (noted as the appropriate numeral in the table above):

1) Data Report #1: A preliminary report of project progress including identification and acquisition of SAV data and information sources, report of initial field surveys. Also, a preliminary description of mangrove & marsh study sites, initial species list and estimates of density and biomass of small fishes and crustaceans from encircling nets in intertidal habitats.

2) Data Report #2: This report will provide the first estimates of the aerial extent and of seasonal variation in SAV. It will also contain the first quantitative preliminary estimates of standing stocks of fishery organisms from SAV. Additionally, this report will contain 6-7 months of data on small fishes and crustaceans from encircling nets in mangroves and brackish marshes along Shark/Harney River as well as associated physico-chemical data. There will be a preliminary summary of the results from the trap nets for large fish. Results of the manatee workshop will also be provided, as will progress on manatee model construction

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PROJECT SUPPORT REQUIREMENTS
Names, expertise of key project staff (* proposed involvement beginning in out-years):
Don DeAngelis, BRD - modeler
Brad Stith, ATLSS manatee model
Jim Reid, BRD - manatee biology, SAV characterization
Dean Easton, BRD - manatee biology, characterization
*Robert Halley, GD - coastal processes, sedimentation
Larry Handley, BRD - remote sensing, SAV mapping
Lynn Lefebvre, BRD - manatee biology, characterization
*Victor Levesque, WRD - estuarine hydrology
Carole McIvor, BRD - aquatic ecology, fish ecology
Michael B. Robblee, BRD - seagrass ecology
Thomas J. Smith, III, BRD - estuarine ecology
*Larry Handley - mapping

Major equipment/facility needs:
Continued operational and technical support as currently provided by BRD (REB), and NPS (Everglades National Park).

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