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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: Paleosalinity as a Key for Success Criteria in South Florida Restoration
Study Start Date: 10/01/2000 Study End Date: 9/30/05
Web Sites: http://sofia.usgs.gov/flaecohist/; http://sofia.usgs.gov/exchange/index.html
Location (Subregions, Counties, Park or Refuge): Everglades National Park, Monroe County
Funding Source: USGS Greater Everglades Priority Ecosystems Science (GE PES) Initiative
Principal Investigator(s): G. Lynn Wingard
Study Personnel: Thomas Cronin; Chuck Holmes; James Murray; Robert Stamm and G.L. Wingard (US Geological Survey); Gary Dwyer (Duke University)
Supporting Organizations: South Florida Water Management District; Everglades National Park
Associated / Linked Studies: Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay; Ecosystem History of the Southwest Coast-Shark River Slough Outflow Area; Monitoring Sub-Aquatic Vegetation through Remote Sensing: A pilot study in Florida Bay.

Overview & Objective(s): There are three primary objectives to this project: 1) Develop a high resolution methodology to analyze the variability in shell chemistry of select marine/estuarine organisms as a proxy to changes in water quality and source, 2) Develop an understanding of the biology of the selected organisms such that the variations in shell chemistry may more accurately reflect the temporal and spatial variability of both water quality and source, 3) Apply this technique to shells found in sediment cores that span the last 100-300 years of South Florida history in order to determine the seasonal variation in salinity and water sources prior to significant human alteration of the environment. These data will provide resource managers with the necessary information to establish targets and performance measures as restoration of more natural timing and delivery of water proceeds.

Status: Research and experiments on objectives one and two have been concluded and reports are in final phase of preparation. Objective three has been completed using ostracode Mg/Ca ratios and a report is currently being generated and will be complete by late summer or early fall. Application of molluscan shell chemistry is more problematic, and can only be applied to core analyses with a number of cautions and under limited conditions. Currently few cores contain material appropriate for these analyses, so this objective will be incorporated into other ongoing studies as ecosystem history of the southern estuaries work proceeds.

Recent Products:
A summary chapter on the Ecosystem History of Florida Bay, with the emphasis on Paleosalinity was generated for the Florida Bay PMC synthesis and has been reviewed for publication in an FMRI bulletin. Two fact sheets were completed in FY05 (FS 2004-3116 and 2004-3141). An oral presentation was given to the Southern Estuaries Sub-Team of the RECOVER Regional Evaluation Team (June 2005).

Planned Products:
Reports on a) the molluscan salinity and temperature tolerance experiments and b) the shell chemistry analyses are in the final stages of preparation and will be completed in FY05. A journal article on ostracode Mg/Ca ratios also is in preparation for submittal in FY05. After the reports are generated, a journal article on the application of molluscan shell chemistry to paleosalinity research will be prepared.

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 goal of the Paleosalinity study is to develop a high resolution method for interpreting short term (less than a decade) changes in salinity from calcareous organisms preserved in cores dating back 100-500 years. The results of this work are applicable to all USGS ecosystem history studies. Specifically this study supports the Florida Bay and Florida Keys Feasibility Study Project and the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study Project, and it provides information relevant to the Combined Structural and Operational Plan (CSOP) and Landscape Modeling projects. This study supports these projects by 1) developing a tool that can be used to understand the predrainage hydrology, including the amount, timing and seasonality of freshwater delivered historically; and 2) providing modelers with data on historic conditions in order to set targets and performance measures that reflect natural hydrologic patterns.

This study supports the Florida Bay and Florida Keys Feasibility Study Project by addressing the questions 1) What are the links between impediment to circulation created by the causeway and the ecology of Florida Bay . . .?" (DOI Science Plan, p. 64), "What are the links between freshwater inflows to Florida Bay and the ecology of the bay?" (p. 65), and "What is the ecological response to hydrologic change?" (p. 66).

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 . . . Taylor Slough . . . prior to drainage and modification . . ." (DOI Plan p. 63), "What are the hydrologic targets needed to mimic historic flows . . . ? (p. 63).

Key Findings:

  1. Synthesis of data from all paleoecology research done in Florida Bay to date has demonstrated that rainfall is the predominant driver of salinity variation in the Bay.
  2. Comparison of Mg/Ca trace element record from sediment core ostracodes to instrumental salinity record from Florida Bay over the last 50 years has demonstrated that Mg/Ca accurately reflects salinity to within 1-4 ppt.
  3. The mollusk Chione cancellata can potentially be used to calculate paleosalinities from the Mg/Ca ratio of the shell layers; however, several cautions are in order. First, Chione do not grow continuously throughout the year, therefore they are not recording an annual history, but our preliminary studies indicate that at least 50% show growth during the summer maximums in salinity and temperature. Second, if only 50% show growth at any one time, we need to either statistically average results when analyzing specimens from cores, or determine some other method of dealing with the potential lack of growth during a given time period. Third, we should limit our analyses to juveniles or sub-adult individuals, or to the juvenile/sub-adult portion of the shell of older specimens.
  4. A statistical method of deriving a single salinity value from molluscan percent abundance assemblage data has been developed and compared to instrumental readings. With additional experimental data on molluscan salinity tolerances this statistical method will enhance accuracy of salinity estimates from cores.

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Last updated: 04 September, 2013 @ 02:08 PM(KP)