|projects > development of integrated sampling of fishes in forested wetlands in south florida with emphasis on food web structure > work plan
U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (GE PES)
Fiscal Year 2005 Study Work Plan
Study Title: Development of Integrated Sampling of Fishes in Forested Wetlands in South Florida with Emphasis on Food Web Structure
Overview & Objective(s):
Forested wetlands, mainly comprised by mangrove and cypress swamps in South Florida, and contiguous marshes formerly functioned as critical feeding and nesting sites for wading birds, populations of which have declined precipitously in coincidence with changes to the hydrology of the region. Human-induced changes have affected the natural variability of environmental conditions through the construction of canals and levees that can either act to drain or flood wetlands. These changes are hypothesized to have negatively affected the production and availability of fish prey for the birds. A major target of restoration is the reestablishment of the natural hydrological conditions in the wetlands. Another alteration to these systems has been the introduction of more than 10 species of non-native fishes.
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 hydrology in the drainage basins, there can be little doubt that the standing stocks of aquatic animals and habitat use have been affected negatively. This study proposal seeks to refine sampling methodology in the forested wetlands, to collect baseline data for aquatic animals to enable comparisons between CERP and non-CERP impacted wetlands, and to begin studies of food-web structure in cypress and mangrove wetlands.
Specific Relevance to Major Unanswered Questions and Information Needs Identified:
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? This includes both systems proposed for study here. The Plan suggests that this question may be examined through baseline studies of fish and invertebrate community sampling. Of course, we also must learn the best way to sample those communities in selected habitats, another objective of this proposal and related CERP-MAP work.
Some elements proposed in this study, although not directly sited within the Southwest Florida Feasibility Study area or the Southern Golden Gates Estates area, will help support the needs of those projects as listed in the DOI science plan because the data we gather in similar habitats of the same ecosystem will be applicable there. Those needs include the identification of key indicators in the aquatic systems. Similarly, simulation models produced using data and rules from this study will be applicable across the Big Cypress ecosystem. 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 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 PES study intends to provide information on those food webs, including such basic questions as: what species utilize those wetlands, what groups 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.
We include additional information on how this study may help answer critical restoration-related questions within each Task description below.
This new study is tightly linked financially and conceptually to CERP-MAP project of McIvor and Lorenz which proposes to test sampling methods and designs in forested wetlands. This PES-proposed study will use those methods and designs to collect baseline data on fish and macroinvertebrate communities at locations likely to be influenced by future CERP activities as well as at unaffected sites that may serve as reference locations. This study will also map the food-web structure of the mangrove and cypress forests to understand the primary sources and pathways of energy flow in those systems. Those data can be compared with future data sets to detect differences in the food webs that may result from CERP actions.
Annual and final reports, oral presentations and posters at appropriate conferences, Fact Sheet, and journal manuscripts.
Title of Task 1: Fish community structure (species composition, numbers, biomass) and food-web structure of fringing mangrove forest wetlands in South Florida
Task Summary and Objectives:
McIvor has 4 years of forest nekton data from 3 sites along the salinity gradient of Shark River, an area open to potential CERP effects. This proposed project in conjunction with the CERP-MAP project of McIvor and Lorenz will continue this long-term data set for the Shark River. Secondly, this new project will phase in sampling of forested nekton along the North River, a reference or non-CERP site. We will begin here with activity-trap arrays, with the goal of adding more quantitative devices in Year 2 as the gear comparisons funded by CERP-MAP proceeds. We will also begin food-web analysis of Shark River sites by measuring stable carbon and nitrogen isotope signatures in selected groups in the food web (see Task 2 below).
Work to be undertaken during the proposal year and a description of the methods and procedures:
Subtask 1: Continue sampling at 3 established sites along Shark River using 2X3 m2 bottomless lift nets and intertidal rivulet nets, 3 times/yr. Subtask 2: Add drift-fence arrays to collect information on fish community composition and fish movements at established Shark River sites. Sample concurrently with Subtask 1. Subtask 3: Add 3 drift arrays along an upstream downstream gradient in fringing mangroves on North River. Subtask 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 task will dovetail closely with the CERP-MAP study of sampling feasibility in forested wetlands being done by McIvor and Lorenz. The work elements will help ensure successful implementation of the MAP because it is important for DOI to determine which aspects of the monitoring components and research topics complement and supplement monitoring efforts of other DOI initiatives. For example, the Florida Bay/Florida Keys Feasibility Study questions what are the ecological responses of indicators such as estuarine fishes and mangrove forest species to hydrologic change? By examining seasonal data on hydrology and fish communities, we should be able to discuss those responses. One question posed in the MAP directly linked to baseline information provided in this task is the effect of sea-level rise on coastal wetlands, tidal creek dynamics, and estuarine productivity. In the mangrove forests, the CERP hypothesis is that higher freshwater flows will sustain high-productivity mangrove estuaries, and a key uncertainty is how much CERP influence will affect that production. We intend, that by sampling at reference and potentially affected sites, that our baseline data will help determine the extent of that influence.
Specific Task Product(s):
- Produce Access and Excel datasets and metadata - continuous throughout study.
Title of Task 2: Big Cypress and Mangrove Forest Food Web Diagnosis
Task Summary and Objectives:
From the sampling described in Task 1 and from the associated CERP-MAP study, we will use tissue samples from about 7 species of several species of In addition to summarizing data on fish/invertebrate food habits from the literature, we will use stable-isotope analysis to trace the food webs in selected mangrove tidal forests and cypress forests.
Work to be undertaken during the proposal year and a description of the methods and procedures
A funded CERP-MAP study (McIvor and Lorenz) 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. This task depends on the CERP-MAP collections to provide tissue samples. Fishes and macroinvertebrate samples will be collected in each region several times across the year using several gear types. We intend to use specimens from that sampling for food-web analysis using stable-isotope signatures. The project technician will assist in all field sampling in the Big Cypress community sampling that is part of the CERP-MAP study of McIvor and Lorenz. This task is dependent on the collections of aquatic animals from that funded study. In addition, the technician will be responsible for curating and cataloging food-web samples taken from the mangrove- and cypress-forest data collections. Under direction of the PIs, the technician will prepare those samples for processing at a university lab. Samples of five specimens, or composite samples, of seven groups of important primary producers, primary consumers, and secondary consumers will be collected at high water, the transition period, and at low water during the routine sampling events in both systems. The groups will represent at least two important chains in the food web. The proposed sampling design for each ecosystem is 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.
Samples will be frozen in the field. In the lab, plants will be dried, ground, and acidified. Animal tissues will be dissected, dried, and pulverized prior to lipid extraction. The isotopic signatures of carbon and nitrogen will be measured. Carbon provides information on primary producers in the food chains while nitrogen isotopes provide information on trophic position. We will try to obtain data on sulfur isotope signatures in a subset of samples to find if those data are informative. All isotope data will be provided to the PIs for analysis and reporting.
There are data on food-web and community structure available for the Everglades marsh, but little information from other major south Florida ecosystems. One new project funded by the Coastal Everglades LTER will examine food webs in the oligohaline zones of Shark River and Taylor sloughs. The work areas we propose in the mesohaline zone of Shark River and in the freshwater Big Cypress are adjacent to the oligohaline and Everglades systems and, in conjunction with those studies, will provide a more comprehensive and integrated view of food webs across these landscapes.
The data derived from this task and associated sampling will provide information listed as needs in the DOI Science Plan and in CERP-MAP documents. 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 plan to conduct baseline data on fish communities and food webs in the forested wetlands of those areas, as well as in reference sites that will not receive CERP effects. Those data will be applicable to meeting information needs in the Southern Golden Gates Estates for monitoring ecological responses to hydrologic change. The DOI Science Plan calls for studies that include expanded sampling of aquatic invertebrates (including crayfish) and fishes. Exotic fish presence is a concern in the progress of restoration. The study will provide data on species composition and relative abundance of those species. If any species is abundant in the system, it will be included in the food-web analysis.
Specific Task Product(s):
- Annual Report - 3 months past first complete study year.
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 04 September, 2013 @ 02:08 PM(KP)