William Loftus (retired)
The Big Cypress Swamp and mangrove ecosystems have been affected by these anthropogenic activities, yet the effects are unclear because of the lack of study. In both ecosystems, there is little quantitative information on the community composition, size-structure, and biomass of fishes and macro-invertebrates because few studies have been carried out there, This is especially true in the forested habitats of those ecosystems. Reasons for lack of study include logistical problems such as access to study areas and difficulties in devising appropriate sampling methods and feasible designs. However, because of the scope of anthropogenic changes in the drainage basins, there can be little doubt that the standing stocks of aquatic animals and habitat use have been affected negatively.
Work planned for FY 2005:
Fish community structure (species composition, numbers, biomass and food-web structure of fringing mangroves forest wetlands in South Florida 1. Continue sampling at 3 established sites along Shark River using 2X3 m2 bottomless lift nets and intertidal rivulet nets, 3 times/yr
2: Add drift-fence arrays to collect information on fish community composition and fish movements at established Shark River sites. Samples taken concurrently with 1 above
3: Add 3 drift arrays along an upstream downstream gradient in fringing mangroves on North River.
4: Collect primary producers (mangroves, benthic microalgae, phytoplankton) and selected consumers (herbivores, detritivores, microcarnivores, piscivores) at 3 Shark River sites to describe the food webs there.
This portion of the project 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.
Big Cypress and mangrove forest food web diagnosis A study to determine sampling gear and perform cross-gear comparisons in two forested wetland systems in south Florida is providing the means to collect baseline fish and invertebrate data at reference and potential CERP-affected sites in the mangroves and cypress regions. The food-web task utilized the CERP-MAP collections to provide tissue samples for analysis, in addition to collections made specifically by task personnel. Fishes and macro-invertebrate samples were collected in each region several times across the year using several gear types. We used stable-isotope analysis to obtain carbon and nitrogen signatures for abundant taxa of primary producers and consumers. Project PIs and technicians collected, curated, and cataloged food-web samples taken from the mangrove- and cypress-forest data collections. Under direction of the PIs, the task technician prepared those samples for processing at the FL International University lab. The sampling design for each ecosystem was to sample in the three seasons in two habitats (Creeks and forests in the mangroves; wet prairie and cypress forests in the Big Cypress) from three locations. Exotic fish presence is a concern in the progress of restoration.. The study provided data on species composition and relative abundance of non-native species in the Big Cypress system, and the abundant non-native fishes in the cypress ecosystem were included in the food-web analysis.
Samples of five specimens, or composite samples, of seven groups of important primary producers, primary consumers, and secondary consumers were collected at high water, the transition period, and at low water during the routine sampling events in both systems. The groups represented at least two important chains in the food web. Samples were frozen in the field. In the lab, plants were dried, ground, and acidified. Animal tissues were dissected, dried, and pulverized. The isotopic signatures of carbon and nitrogen were measured. Carbon provides information on primary producers in the food chains while nitrogen isotopes provide information on trophic position. All isotope data were provided to the PIs for analysis and reporting. The first annual report was submitted in December 2006, and the final report in January 2008.
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.
The food-web work in the PES study ran for two years, from 2005-2007, and included two sets of dry, transition, and wet-season samples from both ecosystems, as well as preliminary data from the spring of 2005. A literature review for stable-isotope work and for sampling methods has been compiled into a working bibliography. An agreement between USGS and FIU was 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. Although much of Southwest Florida lies beyond the range of most CERP projects and models, there are areas of the Big Cypress National Preserve that will be affected by activities on the Big Cypress Seminole Indian Reservation and by Decompartmentalization of WCA 3-A along the L-28 Canal. Levee and canal construction along that boundary is believed to have resulted in diversion of waters away from the eastern Big Cypress and drainage of surface and ground waters. We continue to collect baseline data on fish communities in the forested wetlands of those areas, as well as in reference sites that will not receive CERP effects. Those data will be useful in meeting information needs in the Southern Golden Gates Estates for monitoring ecological responses to hydrologic change.
U.S. Department of the Interior, U.S. Geological Survey
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