Project Summary Sheet

Study Title: Historical Changes in Salinity, Water Quality and Vegetation in Biscayne Bay
Study Start Date: 3/15/02 Study End Date: 9/30/07
Web Sites: http://sofia.usgs.gov/flaecohist/
Location (Subregions, Counties, Park or Refuge): Biscayne National Park, Miami-Dade County, Monroe County
Funding Source: USGS Greater Everglades Priority Ecosystems Science (PES) Initiative; South Florida Water Management District
Principal Investigator(s): G. Lynn Wingard
Study 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 Studies: 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. Also, DOI Landscape Initiative with Biscayne National Park (USGS Lead: Sonya Jones)

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. 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: Analyses of six cores have been completed and compiled with data from cores collected in 1997-98, and a report produced for SFWMD. This was the final obligation for the 2-year contract with SFWMD. Currently, we are conducting additional analyses on samples to refine age models and preliminary interpretations of cores by filling in data gaps. Statistical analyses will be conducted on data from all cores in Biscayne and compared to historical records of outflow, rainfall, etc. Based on results of compilation, we may consider additional core collection to resolve any questions raised.

Recent Products: OFR 03-375 summarized results of first year of analyses for project - published Fall 03. Four reports generated for SFWMD in FY04.
Planned Products: An OFR summarizing results from year two analyses will be published in Fall 04. A fact sheet also will be produced in Fall 04. These will be followed by a series of journal articles summarizing different aspects of the ecosystem history study of Biscayne Bay.

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 Biscayne Bay study is to determine the predrainage hydrology and ecology of the Bay and surrounding wetlands. Specifically this study supports the Biscayne Bay Coastal Wetlands Project and the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study, and it provides information relevant to the Combined Structural and Operational Plan (CSOP), Landscape Modeling, Invasive Exotic Plant Detection, and Monitoring and Aquatic Exotic Animals 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 the bay 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; 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; and 5) by determining the timing of introduction and spread of exotics in the Biscayne Bay ecosystem and the coincident changes in the native species.

This study supports the Biscayne Bay Coastal Wetlands Project by addressing the questions “How much freshwater, and in what seasonal patterns, was delivered historically to Biscayne Bay?” (DOI Plan, p. 63), “What are the links between hydrology and ecology in the Biscayne Bay coastal wetlands?” (p. 64), and “What are the key indicators of natural ecological response . . .” and “what are the baseline conditions of the indicators?” (p. 66). The data generated by this project are particularly valuable because they provide 100 to 500 years worth of data on changes to the system.

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 . . . Biscayne Bay prior to drainage and modification . . .” (DOI Plan p. 63), “What are the hydrologic targets needed to mimic historic flows . . . ? (p. 63).

In addition, the study contributes to the Combined Structural and Operational Plan (CSOP) and Landscape Modeling projects 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).

Key Findings:

1. The salinity of Biscayne Bay has been steadily increasing over time in all nine cores examined to date. Although the timing and onset of increased salinity varies at the different core sites, there are no exceptions to this trend.
2. Sites in both central and southern Biscayne Bay show indications of increasing marine influence at the sites. These trends could be a result of rising sea level, of changes to the natural flow of fresh water or both, but the timing of changes at some of the near-shore sites suggests both factors are involved.
3. In near shore areas, distinct, but site specific, changes in freshwater influx over time have occurred, and our data suggest that some sites we assumed had historic point-source inflow of fresh water did not, even prior to human alteration of the natural environment. Wetlands sites in very close proximity to each other have historically been affected by very localized hydrologic regimes.
4. Implications for managers: 1) Biscayne Bay appears to be evolving toward a more marine environment and sea-level rise should be factored into the planning process; and 2) generalized performance measures and targets for the near-shore and wetlands areas may not reflect the natural variability seen at these sites.