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projects > ecosystem history of the southwest coast-shark river slough outflow area
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Project Summary Sheet
Fiscal Year 2006 Study Summary Report
Study Title: Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area
Overview & Objective(s): One of the primary goals of the Comprehensive Everglades Restoration Plan (CERP) is to restore the natural flow of water through the terrestrial Everglades and into the coastal zones. Historically, Shark River Slough, which flows through the central portion of the Everglades southwestward, was the primary flow path through the Everglades Ecosystem. However, this flow has been dramatically reduced over the last century as construction of canals, water conservation areas and the Tamiami Trail either retained or diverted flow from Shark River Slough. The reduction in flow and changes in water quality through Shark River have had a profound effect on the freshwater marshes and the associated coastal ecosystems. Additionally, the flow reduction may have shifted the balance of fresh to salt-water inflow along coastal zones, resulting in an acceleration of the rate of inland migration of mangroves into the freshwater marshes. The objectives of this project are to document impacts of changes in salinity, water quality, coastal plant and animal communities and other critical ecosystem parameters on a subdecadal-centennial scale in the southwest coastal region (from Whitewater Bay, north to the 10,000 Islands), and to correlate these changes with natural events and resource management practices. Emphasis will be placed on 1) determining the amount, timing and sources of freshwater influx (groundwater vs. runoff) into the coastal ecosystem prior to and since significant anthropogenic alteration of flow; and 2) determining whether the rate of mangrove and brackish marsh migration inland has increased since 20th century water diversion and what role sea-level rise might play in the migration.
Status: Twenty-two cores have been collected from 11 sites in the southwest coastal area along transects leading from the inner bays out to the coastal marine environment. Carbon 14 and Pb-210 analyses have been completed on the 2004 cores from the inner bays, and samples have been processed, sorted, and a preliminary assessment of environments based on mollusks completed. Detailed faunal and floral abundance counts are underway for the 2004 cores. Five of the six 2005 cores have been processed and a preliminary assessment of environments based on mollusks completed. Samples for carbon-14 analyses have been selected, and will be sent for analyses in October 2006. Samples from the processed 2005 cores are currently being sorted and counted. At this time, no additional core collection is planned, but we will conduct additional modern sampling to refine our modern analog data set.
Schill, W.B., 2006, Assessment Of Historical Ecological Changes Using A Molecular Approach: Greater Everglades Ecosystem Restoration Conference, June 2006.
Wingard, G.L., Cronin, T.M., Holmes, C.W., Willard, D.A., Budet, C., and Ortiz, R., 2005, Descriptions and Preliminary Report on Sediment Cores from the Southwest Coastal Area, Everglades National Park, Florida: U.S. Geological Survey, OFR 2005-1360, 28 p. [Available online at http://sofia.usgs.gov/publications/ofr/2005-1360/]
Wingard, G.L. and project members, 2006, Ecosystem History of Florida Bay and the Southwest Coast: Comprehensive Annual Report to Everglades National Park, 112 pp.
Wingard, G.L., Budet, C.A., Ortiz, R.E., Hudley, J.W., and Murray, J.B., 2006, Descriptions and Preliminary Report on Sediment Cores from the Southwest Coastal Area, Part II Collected July 2005, Everglades National Park, Florida: US Geological Survey Open-File Report 2006-1271, 30 pp. [In review]
Open-File reports will be generated as analyses on individual cores are completed. Results will then be compiled for journal publications. Oral presentations at national meetings and to clients will take place periodically.
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) [See Plan on SOFIA's Web site: http://sofia.usgs.gov/publications/reports/doi-science-plan/]:
One of the primary DOI activities discussed in the DOI Science Plan is to "ensure that hydrologic performance targets accurately reflect the natural predrainage hydrology and ecology" (DOI Science Plan, p. 14). The primary goal of the Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area study is to determine the predrainage hydrology and ecology of the southwest coastal environment. Data from this project are being used by the Southern Estuaries Sub-Team (SET) of the Regional Evaluation Team (RET) of RECOVER to set performance measures (PMs) for the Whitewater Bay area.
Additionally, this study supports the Additional Water for Everglades National Park, the Southern Golden Gate Estates Hydrologic Restoration, and the Southwest Feasibility Study Projects. This study supports these projects by 1) conducting research to understand the predrainage hydrology, including the amount, timing and seasonality of freshwater delivered to southwest Florida historically; 2) examining the historical environmental conditions, including the linkage between hydrology (water quality and quantity), ecology, and habitats; 3) providing the modelers with data on historic conditions in order to set targets and performance measures that reflect natural hydrologic patterns; and 4) providing long-term historical data on trends and cycles within the biological component of the ecosystem that can be forecasted to predict the effects of implementation of hydrologic restoration on the ecology of coastal communities.
This study supports the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study by addressing the questions "What were the physical and ecological conditions in . . . Shark River Slough . . .prior to drainage and modification . . ." (DOI Plan p. 63), "What are the hydrologic targets needed to mimic historic flows . . . ? (p. 63). This study supports the Southern Golden Gate Estates Hydrologic Restoration Project by providing long-term (100-500 years) data on natural hydrologic patterns that can be used to set targets for freshwater inflows (p. 50). In addition, information on long-term changes in the biota and ongoing studies to develop our modern proxy database (used for core interpretation) will provide baseline data on the ecological responses of communities and species (p. 51). This study supports the Southwest Feasibility Study Project by providing predrainage hydrologic and ecologic conditions that can be used to set the hydrologic targets (p. 50). The results of the core analyses will provide data on temporal and spatial patterns within the estuaries and the linkage between hydrologic conditions and ecological responses; this information can be used by the modelers (p. 50) and to determine what faunal or floral species might be used as key indicators (p. 51).
In addition, the study contributes to the Landscape Modeling project by providing historical ecological data on trends and cycles that can be forecasted to predict the effects of implementation of hydrologic restoration on the ecology of coastal communities. This addresses questions of the impact of increased flow (p. 63), and expected faunal and floral responses (p. 64, p. 79, p. 80). The study also contributes to the Invasive Exotic Plant Detection and Monitoring and Aquatic Exotic Animals Projects by determining the temporal and spatial distribution of exotics and changes in native species coincident with introduction (p. 118).
Initial examination of cores collected in 2004 indicates a long depositional history (1000-2000 years), slow sedimentation rates, and distinct changes in the environment occurring over time. Preliminary examination of the 2005 cores has provided a preliminary model of general patterns of freshwater flow over time for this area. Throughout the time period recorded by the cores, flow to the southwest coastal area has been predominantly through the Shark River channels, diminishing to the north toward the Lostmans River system. The Lostmans system was less influenced by freshwater flow and more emergent than the two systems to the south. The mouths of the river channels have persistently been zones of mixed estuarine environments, with pulses of freshwater periodically reaching the mouth of the Harney and Shark River systems. The lower portions of the mid-system cores from the Harney and Shark Rivers were deposited in freshwater environments, but a change in the system caused a shift towards more estuarine conditions. The core from Roberts River, which empties into Whitewater Bay, shows a clear transition from a freshwater/terrestrial environment near the bottom of the core to a nearshore estuarine environment at the top of the core.
U.S. Department of the Interior, U.S. Geological Survey
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