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Project Summary Sheet

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

Fiscal Year 2006 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 (Extended into 2007)
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 GE PES
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: Continuing study
Principal Investigators: Carole McIvor and William F. Loftus
Study Personnel: National Audubon Society CESU cooperators: Jerome Lorenz, Shawn Liston, David Green, and a technician; 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 F. Loftus, P.I.)

Overview & Objective(s): Comprised mainly by mangrove and cypress swamps in southern Florida, forested wetlands and their contiguous marsh wetlands once functioned as critical feeding and nesting sites for wading birds, populations of which have declined precipitously in coincidence with regional hydrological changes. Natural hydrological variability within the wetlands has been altered during the past 100 years by the construction of canals and levees. Those changes are hypothesized to have negatively affected the production and availability of fish and invertebrate prey for the birds. Reestablishment of natural hydrology is the major goal for restoration of the wetlands.

To detect changes in aquatic communities from CERP restoration projects, baseline data are needed before and after restoration actions. Monitoring data must be collected using the most efficient, cost-effective methods and sampling design for the habitat. In this study, we are testing methods for measuring community parameters for fishes and aquatic invertebrates, and their food webs, in relation to hydrological regimes. This study is part of a broader, cooperative effort between National Audubon, FIU, and USGS. It is tightly linked financially and conceptually to the CERP-MAP projects of McIvor, Lorenz, and Trexler designed to test sampling methods and designs in forested and graminoid wetlands. This PES study is divided into two tasks, 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 & environmental factors. Task Two depends on samples of aquatic animals from the mangrove and cypress study funded by CERP-MAP to examine food-web structure in the two forested wetlands using stable-isotope analysis for carbon and nitrogen in biotic tissues. Data from both tasks will be made available for input into simulation models used to plan and evaluate restoration actions.

Status: Funding for the first year of this PES study was received in late December 2004, and a portion transferred to Ft. Lauderdale in May 2005 for the food-web work. USGS personnel have worked closely with our National Audubon Society and ETI cooperators in sampling in the cypress and mangrove systems, and in collecting and processing stable-isotope samples from both systems for analysis. We installed water-data recorders in 2006 at each cypress sampling site. Community sampling at the mangrove-forest sites was performed in July and November 2005, and in January and May 2006. Community sampling at the cypress sites was conducted in July, October, and December 2005, and in February and April of 2006. Exploratory sampling for food-web targets was done in the cypress in June 2005 and in the mangroves in July 2005. Full-matrix sampling for stable-isotope samples was planned for October 2005 but was interrupted by the passage of Hurricane Wilma. Complete matrix samples were taken from cypress sites in December, 2005 and in February and April, 2006 to match high, transitional, and low water conditions. Stable-isotope samples from the mangrove sites were collected in November, 2005 and in January and May, 2006 to correspond to similar water conditions. After collection, the frozen specimens for isotope analysis were identified, weighed, and measured in the lab, tissues dissected and dried, then prepared for analysis using a mass spectrometer at Florida International University. Labeled samples were taken to the FIU for analysis, as set out in the CESU agreement with FIU, written in FY05.

Data returned from FIU is entered into a spreadsheet to produce descriptive statistics and graphics prior to further statistical analyses. To date, all animal samples from cypress habitats have been processed; samples from mangroves have been processed through the January sample. We have received data from the FIU lab for both systems for the 2005 samples and the early 2006 samples. We continue to update our literature review for stable-isotope work and for sampling methods into the working bibliography.

The food-web work proposed in the PES project depended on a dry-season and a wet-season sample from BCNP collected by the CERP-MAP study. Because funding by CERP-MAP to National Audubon for sampling in cypress habitats was not received until May 2005, we were unable to adhere to the original project schedule. We have planned for two years of dry, transitional, and wet-season samples, but because no samples were collected in the 2005 dry season, that sample was moved forward to 2006. We have revised the original project schedule to insure that all the work we proposed will be accomplished in 2007.

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 bibliography for sampling methods and food-web work in cypress and mangrove habitats has been produced. Presentations of project progress were made in October 2005 and at an AT meeting in March 2006. Project results were presented at science conferences in FY06; published abstract titles are listed below.

Green, D. P., W. F. Loftus, And C. C. Mcivor. 2006. Estimating Production Origins And Trophic Placement Of Biota In Forested-Wetland Food Webs: Preliminary Results From Stable Isotopes. GEER Meeting, Orlando.

Green, D. P. J., J. C. Trexler, T. E. Philippi, J.J. Lorenz, and C.C. McIvor. 2006. 'Can't get there from here': Hydrological connectivity impacts temporal and spatial patterns of fish community structure. LTER All-scientists Meeting, Miami.

Silverman, N.L., C.C. McIvor, J.M. Krebs, and V.A. Levesque. 2006. Hurricane-induced conversion of mangrove forest to mudflat: impacts on nekton, Big Sable Creek, Florida, USA. Presentation. First International Symposium on Mangroves as Fish Habitat, Miami, FL, April 19-21, GEER Meeting, Orlando.

Planned Products: Annual and final reports in 2006-7, oral presentations and posters at conferences, and Fact Sheets and journal manuscripts at the end of the study. See attached "Revised Reporting Plan."

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. The first step in doing those studies is to test the most efficient ways to sample those communities. This study supports several projects listed in the DOI Plan 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 these forested wetlands will have application in sampling systems elsewhere. Those needs include the identification of key indicators in the aquatic systems. Specifically, we will provide data by monitoring responses of fishes to help understand the effects of different hydrologic regimes in restoring and maintaining ecosystem function. We shall provide 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 premise that hydrological effects will be seen in the food webs leading to higher vertebrates. One Adaptive Management question in CERP is whether the restoration of Natural System Model conditions will 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 forested wetland 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? Without this basic ecological information on community structure, it will be difficult to predict how CERP actions may influence these systems.

Key Findings:

  1. Composition of the forage-fish community using flooded mangrove forests along Shark River is largely explained using a combination of salinity (mean, variance), and depth of tidal flooding.
  2. We have identified fish species that will be useful for monitoring hydrologic change in mangrove forests along Shark River.
  3. We have tested and identified several sampling techniques that are being applied side-by-side in both forested-wetland types to collect aquatic animals, which will be appropriate for monitoring in community and food-web studies.
  4. We have successfully sampled target species that comprise major density or biomass pools in each ecosystem. Preliminary data indicate that we identified the main primary producers in cypress, but appear to be missing an important carbon source in the mangrove forests. We are consulting with an algal specialist to investigate other sampling methods to identify other sources.
  5. As a result of the first sampling data for stable isotopes, we are collecting data to determine whether the cypress food web is subsidized by carbon sources from graminoid wetlands surrounding the cypress. Fishes and invertebrates moving seasonally from local marshes into cypress habitat might be the agents for such subsidies.
  6. Food-web components (species) in the cypress habitat are similar to those in the Everglades marsh, although the nitrogen signatures for those organisms in cypress are lower overall than for those species in marshes. Carbon signatures are lower in the same trophic groups in cypress vs. mangrove areas, indicating differences in the primary-producer signatures at the food-web base.




2006 June  
Oct Field - cypress
Nov Field - mangrove
2007 Jan  
Feb Field - cypress
Field - mangrove
Apr Field - cypress
May Field - mangrove
Sep FINAL REPORT 9/30/07
Dec Submit Food-web MANUSCRIPT to journal

* A single annual report will be produced for the PES and MAP projects in 2006 - other reports will be completed for each project by the respective P.I..

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