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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Science Initiative (Place-Based Studies)

Fiscal Year 2003 Project Summary Report

Project Title: Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay

Project Start Date: 3/15/02 Project End Date: 9/30/05

Web Sites:

Location (Subregions, Counties, Park or Refuge): Biscayne National Park, Miami-Dade County, Monroe County

Funding Source: USGS's Greater Everglades Science Initiative (PBS); South Florida Water Management District

Principal Investigator(s): G. Lynn Wingard

Project Personnel: Thomas Cronin; Debra Willard; Chuck Holmes; William Orem; James Murray; Robert Stamm; Joseph Murray, Carlos Budet, Jessica Albeitz, Marci Marot; US Geological Survey. Gary Dwyer, Duke University. Scott Ishman, Christopher Williams; University of Southern Illinois.

Supporting Organizations: South Florida Water Management District; Biscayne National Park

Associated / Linked Projects: Paleosalinity as a Key for Success Criteria in South Florida Restoration; 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): The objectives of this project are to examine in broad context the historical changes in the Biscayne Bay ecosystem at selected sites on a decadal-centennial scale, and to correlate these changes with natural events and anthropogenic alterations in the South Florida region. Specific emphasis will be placed on historical changes to 1) amount, timing, and sources of freshwater influx and the resulting effects on salinity and water quality; 2) shoreline and sub-aquatic vegetation; and 3) the relationship between sea-level change, onshore vegetation, and salinity. In addition, a detailed examination of historical seasonal salinity patterns will be derived from biochemical analyses of ostracodes, foraminifers, molluscs, and corals. The corals will allow us to compare marine and estuarine trends, examine the linkage between the two systems, and will provide precise chronological control. Land management agencies (principally SFWMD, ACOE and Biscayne NP) can use the data derived from this project to establish performance criteria for restoring natural flow, and to understand the consequences of altered flow. These data can also be used to forecast potential problems as upstream changes in water delivery are made during restoration.

Status: Initial analyses of cores collected in Spring 2002 have been completed, compiled with data from cores collected in 1997-98, and a report produced. Analyses of corals and water chemistry completed by P. Swart, UM-RSMAS. New core sites were selected in consultation with the clients and three new cores collected in June 2003. These cores will be processed in the summer of 2003.

Recent & Planned Products: Completed 12 reports for SFWMD between 3/02 and 3/03. Abstract and talk for GEER conference. OFR summarizing results is in review and should be published as CD-Rom by end of FY03.

Relevance to Greater Everglades Restoration Information Needs: One of the primary restoration goals identified by the South Florida Restoration Task Force - to "get the water right." The Comprehensive Everglades Restoration Plan (CERP) Biscayne Bay Coastal Wetlands Project (BBCW) has specifically identified the importance of understanding freshwater flow into Biscayne Bay and the changes incurred due to alterations in flow. The USGS Science Plan for south Florida has identified five primary science objectives (SO) to address the needs of restoration and this project meets 3 of those objectives for Biscayne Bay:

SO2. Determine the historical setting of the greater Everglades ecosystem
SO3 Establish baselines and variations for restoration targets
SO5 Predict ecosystem response to anthropogenic and natural change

This project fulfills these objectives by providing information on natural patterns of change in salinity, water quality, vegetation, and benthic fauna in Biscayne Bay and the nearby wetlands over the last 100-500 years. Data on historical patterns of change over centennial and decadal time scales allows CERP project managers to set realistic restoration targets that take natural patterns of change into consideration, and provides predictive capabilities on how the system will respond to future changes.

Key Findings:

  • The salinity of central Biscayne Bay has become increasingly marine and increasingly stable over the last century.
    • At No Name Bank, prior to approximately 1915, the inter-annual and decadal salinity fluctuations appear to have been greater than after 1915 when salinities stabilized at that site.
    • Continental shelf influence on the sites has increased during the 20th century.
    • There is no indication of inter-decadal salinity extremes and periods of hypersalinity are not in evidence.
  • Card Bank has experienced relatively large swings in salinity over multi-decadal and centennial timescales, compared to central Biscayne Bay, but marine influence at the site has increased over the last century.

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