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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES) Initiative

Fiscal Year 2005 Study Summary Report

Study Title: Development of Integrated Sampling of Fishes in Forested Wetlands in South Florida with Emphasis on Food Web Structure
Study Start Date: December 2004 Study End Date: December 2006
Web Sites: http://sofia.usgs.gov/projects/fish_sample/
Location (Subregions, Counties, Park or Refuge): FL, Collier & Monroe Counties; Big Cypress NP, Everglades NP
Funding Source: USGS Greater Everglades Priority Ecosystems Science (GE PES) Initiative
Other Complementary Funding Source(s): (Development and Testing of Protocols for Sampling Fishes in Forested Wetlands in Southern Florida (CERP - MAP, McIvor and Lorenz, 2004-2006)
Funding History: New study
Principal Investigators: Carole McIvor and William F. Loftus
Study Personnel: Jerome Lorenz and three National Audubon Society (NAS) CESU cooperators; ETI contractors N. Silverman, K. Kuss; Joel Trexler, FIU Cooperator.
Supporting Organizations: Everglades National Park (ENP), Big Cypress National Preserve (BCNP), Florida International University (FIU), University of South Florida (USF)
Associated / Linked Studies: Role of marsh-mangrove interface habitats as aquatic refuges for wetland fishes and other aquatic animals (MAP, William Loftus, P.I.)

Overview & Objective(s): Forested wetlands, mainly comprised by mangrove and cypress swamps in south Florida, and their contiguous marshes once functioned as critical feeding and nesting sites for wading birds, populations of which have declined precipitously in coincidence with regional hydrological changes. Human-induced changes have affected natural hydrological variability through the construction of canals and levees. These changes are hypothesized to have negatively affected the production and availability of fish prey for the birds. Reestablishment of the natural hydrological conditions in the wetlands is the major goal of restoration. To detect changes in fish and invertebrate communities from CERP restoration projects, baseline data are needed before and after restoration actions. Those data must be collected using the best methods and sampling design for the habitat. The data collected here will examine the habitat relationships of fishes and aquatic invertebrates, major prey for many predatory birds and reptiles, and their food webs, with relation to hydrological regimes. This study is part of a broader, cooperative effort between National Audubon Society (NAS) and USGS PES. It is tightly linked financially and conceptually to the CERP-MAP project of McIvor and Lorenz, designed to test sampling methods in forested wetlands. The USGS PES study is divided into two tasks that are both dependent on the overarching objective of refining sampling methodology in the forested wetlands. Task one is aimed at collecting baseline data to quantify species composition, density, and biomass of fishes and crustaceans in intertidal mangrove forests along the salinity gradient in Shark River, and to relate these distributional patterns to hydrological and environmental factors. Task two depends on samples of aquatic animals collected from the mangrove work, and from the cypress work done by the CERP-MAP study, to examine food-web structure in those wetland habitats. Data from both tasks will be provided for input into simulation models used to plan and evaluate restoration actions.

Status: Funding for this PES study was received in late December 2004. Sampling at the mangrove-forest sites was performed in January and April 2005. Exploratory sampling for food-web targets in the mangroves was also done at those times. Reconnaissance and preparations for deploying three drift-fence arrays were made in April/May 2005. Following a permit modification, three drift-fence arrays were set up at Watson River, a control site for Shark River in May 2005; the other three are planned for Shark River this summer. Sampling was done in July 2005 and will be repeated in November; stable-isotope samples were collected in July. To accomplish the food-web work for this PES study, a cooperative agreement between NAS and USGS was written and executed in 2005. USGS will assist in sampling in BCNP, and will collect and process stable-isotope samples from both the mangrove and cypress habitats. Position descriptions for project personnel were written, and the positions filled with qualified applicants experienced in sampling in south Florida. A literature review for stable-isotope work and for sampling methods has been compiled into a working bibliography updated frequently. The food-web work proposed in the PES study depends on a dry-season and a wet-season sample from BCNP collected by the CERP-MAP study. Unfortunately, funding by CERP-MAP to NAS for sampling in cypress habitats was not received until May 2005. However, that was non-consequential because the site visit in April to deploy additional sampling gear found all sites dry. Next dry season, we will target February for the low-water sample. We have planned for two years of dry and wet-season samples in this study. Because no samples were collected in the dry season of 2005, that sample will have to be moved forward to next winter. A community sample in BCNP was taken in July 2005; the next samples, using drop traps, drift-fence arrays, and electrofishing, are scheduled for October and December 2005. The wet-season isotope sample for 2005 will be taken in October when animal populations have recovered from the spring drought. Exploratory sampling for aquatic biota for the stable-isotope work was done in June 2005 in BCNP, as the sampling sites re-flooded. At that time, the field-deployed sampling installations were also checked. An agreement between USGS and FIU has been approved to allow cooperation on the stable-isotope analysis, so that results will be comparable with previous studies and can be incorporated with them to obtain a landscape-level depiction of aquatic food webs in the Greater Everglades.

Recent Products: Task one is a continuation of work that began in 2000, which has produced an Access database of fish species, numbers and biomass collected in fringing mangrove forests in Shark River. Data from this study's collections have been added to the database. A poster of work from Task one was presented at the FISC Science Conference in May 2005. Because Task two is tied to work with NAS cooperators, a cooperative agreement describing that work and transferring funds to accomplish it was written and executed in 2005. A work plan for the stable-isotope work in Task two was also peer-reviewed and refined. A cooperative agreement with FIU for stable-isotope work was approved. A bibliography of sampling methods and food-web work in cypress and mangrove habitats has been produced.

Planned Products: Annual and final reports, oral presentations and posters at appropriate conferences, and a Fact Sheet and journal manuscripts at the end of the study.

Specific Relevance to Information Needs Identified in DOI's Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida (DOI's Everglades Science Plan):

The major question from the DOI Science Plan addressed by this proposal is: What are the effects of hydrologic changes on the Everglades natural system, including both of these forested-wetland systems. The Plan suggests this question be examined through baseline studies of fish and invertebrate-community sampling. We must learn the best way to sample those communities in particular habitats. This study supports several of the projects listed in the DOI science by providing data on ecological responses of the fish community to CERP-induced changes to hydrology within BCNP and the mangroves of ENP (thereby linking this study to the agency mission of assisting in the management of DOI property). Sampling methods devised for use in these forested wetlands will also have application in sampling aquatic animals in other systems. Those needs include the identification of key indicators in the aquatic systems. Specifically, we can provide data to help understand the effects of different hydrologic regimes and ecological processes on restoring and maintaining ecosystem function by monitoring responses of fishes, and by providing ecological information to models to predict trophic- or species-level responses to habitat changes. The mangrove forests downstream of Shark River Slough are very likely to be affected by those CERP actions intended to deliver more freshwater to the estuaries.

In both ecosystems, CERP restoration goals are based on the ecological premise that hydrological effects will be seen in the food webs leading to higher vertebrates, especially alligators and wading birds. One of the Adaptive Management questions in CERP is whether the restoration of Natural System Model conditions achieve the objective of restoring aquatic food webs that support reproducing populations of higher vertebrates, and, if not, how and to what extent do we modify the physical structure and hydrology of the system to accomplish that? Unfortunately, that premise and strategy may be difficult to test and manipulate because food webs in both systems are so poorly defined. This study will provide information on those food webs, including what species utilize those wetlands, which constitute the major biomass pools, and which primary producers support those communities?

Key Findings:

  1. Composition of the forage-fish community using flooded mangrove forests along Shark River is largely explained by a combination of salinity (mean, variance), and depth of tidal flooding.
  2. A specialized fish, the mangrove rivulus (Rivulus marmoratus), a Species of Special Concern in Florida, is a common forest-floor inhabitant along the entire salinity gradient sampled in Shark River, a fact that may contribute significantly to the decision about whether to list it as a federally protected taxon.
  3. Because there are locations in each forested wetland likely to experience greater and lesser changes to the hydrologic regime during CERP projects, we deployed sampling gear using a design of multiple plots within sites allocated to both types of locations.
  4. We identified several techniques for sampling that we are applying side by side in both forested wetland types for gear comparisons, and in community and food-web studies. Some require modifications to increase effectiveness.
  5. Wet-season collections of specimens for isotope analysis were collected during community sampling, and were frozen in the field prior to processing and analysis. Low densities will require additional sampling.

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