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Ecosystem History of Biscayne Bay and the Southeast Coast

Project Proposal for 1999


PROJECT TITLE: Ecosystem History of Biscayne Bay and the Southeast Coast.

GEOGRAPHIC AREA: Biscayne Bay, South Florida

PROJECT END DATE: September 2000

PROJECT CHIEF: Scott E. Ishman
Eastern Region/Geologic Division/Eastern Region National Cooperative
Geologic Mapping Team
E-mail: sishman@usgs.gov
Phone: (703) 648-5316
FAX: (703) 648-5420
926A National Center, Reston, VA 20192

PROGRAM ELEMENT: Element 3: Modeling and Support Studies for Southern Inland Coastal Systems of Eastern Dade County and Biscayne Bay.

TASKS: Task 3.6: Ecosystem History of Biscayne Bay and the Southeast Coast.


Project Summary: The quantity and quality of water delivered to Biscayne Bay has been altered, affecting the salinity and nutrient supply and introducing toxic components into Biscayne Bay. The project will determine the ecosystem variability and linkages between ecosystem changes and natural and human causes, resulting in useful information for restoration efforts and future monitoring.

Potential Impacts and Major Products: This project will result in a reconstruction of the fresh water flow, salinity, nutrient and substrate (sea grass) histories of Biscayne Bay, as well as the vegetation and burn history of the coastal mangrove environment. These data will be useful for the tasks of setting restoration objectives, testing circulation models and modeling future outcomes of land and water management decisions, priorities established for the Fragile Environments Program. The success of this project will establish tried methodologies for application to restoration of other Fragile Environments within our Nation. Spatial reconstructions of environmental conditions for the last 150 to 200 years will be used to produce synoptic maps of salinity, nutrient and substrate conditions for Biscayne Bay. The data will be compiled and presented in a summary publication on the ecosystem history of Biscayne Bay. These data will provide land and water-use managers with information necessary to set restoration targets, supply circulation modelers with control points to test their models, and locate sites at which restoration objectives can be monitored.

Project Objectives and Strategy: The objectives of this project are: 1) to determine the spatial variability in the distribution of modern biota (foraminifera, ostracodes, molluscs, diatoms and palynomorphs) in Biscayne Bay, and how these distributions relate to the present environmental conditions (fresh water input, salinity, nutrient supply, sea grass and contaminants) in the Bay; 2) apply the modern biotic and environmental associations and geochemical data to biotic and geochemical data from downcore sediments to interpret the temporal variability in the measured environmental conditions; and 3) date the cores using
210Pb to determine the timing of environmental changes interpreted, and relate the changes to historical events of South Florida.
This project uses faunal (foraminifera, ostracodes, and mollusks), floral (palynology and diatoms), and geochemical (stable isotopes and trace element geochemistry) data to determine the ecosystem history of Biscayne Bay. Surface sediments collected from sites within Biscayne Bay (Figure 1) are analyzed for their faunal and floral compositions. These data are correlated to water column data (temperature, salinity, pH, dissolved oxygen, nutrients and redox potential) collected at each collection site, and groundwater data (salinity, nutrient, stable isotope and trace element) collected at specific sites. Calcareous shells of living organisms are analyzed for their trace element composition (Duke University). In addition surficial sediment geochemistry is currently being conducted by NOAA on samples collected near, or at many of the ecosystem sites. Quantitative analyses of these data will be used to determine controls on the modern faunal and floral distributions in the bay, identify organisms as useful environmental indicators, derive trace element (Mg/Ca ratio) calibration equations for modern bay salinities and temperatures, and determine the source areas for specific submarine groundwater flows into the bay.
    Historical changes in the environment are assessed from duplicate sediment cores ranging from one to two meters long collected along two to three transects within Biscayne Bay (Figure 1). The cores are described, and dated using 210Pb (Chuck Holmes, USGS, Coastal and Marine). Samples are collected at two centimeter intervals down the core for faunal, floral, and geochemical analyses. The faunal and floral data is compared to the results from the modern faunal and floral distribution analyses, and the modern trace element calibration equations are applied to downcore trace element data. These results are used to determine historical changes in the ecosystem and environmental conditions controlling these changes. Correlation between significant changes observed in the cores and historical records of change in South Florida will provide useful information on causal mechanisms, natural or human-induced, of ecosystem change in Biscayne Bay.
    Surficial and downcore sediment sieved residues are housed in the Calcareous Laboratory, USGS, Reston, VA and available for additional analyses. The modern distribution data for the various biotic component analyses are documented in USGS Open-File Reports along with descriptions of cores collected for the project.

Collaborators/Clients: Surficial sediment sampling is conducted in collaboration with Metro-Dade Department of Environmental Resources Management (DERM) as part of their monthly BayRun water quality sampling program, and will continue on a seasonal basis (bi-annually) through December 1997. Logistical support in Biscayne Bay for the surficial sampling is provided and supported by Metro-Dade DERM. Logistical support on the bay for coring is provided by Gene Shinn, USGS, CCMG in St. Petersburg. Faunal and floral analyses is conducted at the USGS, Reston. Radiometric isotope dating is conducted by Cbuck Holmes, USGS, WRD, St. Petersburg. Trace element analyses of calcareous organisms is conducted by Gary Dwyer at Duke University. Pore water and sediment geochemistry is conducted by Bill Orem USGS, Reston, VA. Data and information is being exchanged with: Gene Shinn, Vincente Quinones-Aponte and Richard Curry (Biscayne National Park) to determine the effects of groundwater seepage on the benthic ecosystem; and Bob Halley, USGS, CCMG, to relate faunal, floral and trace element historical records to stable isotopic records of change in the short cores. DERM requests information regarding the historical record of ecosystem change and burn frequency in and around Biscayne Bay in order to have a baseline from which they can make land and water use policy decisions. The Army Corps of Engineers (ACOE) is interested in building a water supply model for Biscayne Bay; our data will determine variation in water quality and quantity over time. National Oceanic and Atmospheric Administration (NOAA) is studying the effects of multiple stresses on the southern portion of the bay, and the amount of toxic substances in the surficial sediments. This project will provide a historical perspective on faunal, floral and geochemical (including trace metals) changes over the last 100-150 years. Information provided by this project will assist the National Park Service in making management decisions for Biscayne National Park. Other cross-linkages with USGS, WRD and GD projects are expected to occur.


ActivitiesFY 99FY 00

FY 1999 Deliverables/Products:

  • Progress reports on the modern faunal and floral trace element calibration of calcareous organisms. Reports will be produced as U.S. Geological Survey Open-File.
  • Initial reports on the faunal and floral distributions, and trace element record in the short cores. Reports will be produced as U.S. Geological Survey Open-File Reports at the completion of the downcore analyses of each short core.
  • Updated Fact Sheet on the Ecosystem History of Biscayne Bay and the Southeast Coast.
  • Map (hard and digital copies) describing the modern distributions of faunal and floral elements in Biscayne Bay.
  • Maps (hard and digital copies) describing changes in the ecosystem through time.
  • Digital database describing the modern distribution of plants and animals in the bay.
  • Digital database of the downcore faunal, floral and trace element data.
  • Synthesis document on the ecosystem history and evolution of Biscayne Bay.

Planned Outreach Activities: Contributions toward the production of posters, briefing boards and text for Congressional hearings. Information supplied for the Ecosystem Home Page. Visual materials supplied to managers for presentations on the Ecosystem History Projects. Planning and contribution of display for the Biscayne National Park Visitorís Center.

New directions for FY 1999: None


FY 1998 Accomplishments and Outcomes, Including Outreach:

  • A well defined ecosystem history record was derived from core MB 1 collected from Manatee Bay, Barnes Sound, Florida. The record shows a gradual increase in salinity from the late 1800ís to recent with definitive environmental changes occurring at ~1910, 1940, and in the late 1980ís. These change can be correlated with the completion of the Flagler Railway, construction of the canal and levee system, and water management practices related to C-l 11 canal, repsectively.
  • Two shallow sediment cores were collected from the wetland area to the immediate south of Military Canal. The cores were collected in collaboration with Metro-Dade Department of Environmental Resources to evaluate historical changes associated with the presence of Military Canal and the development of Homestead Airforce Base.
  • Provided materials for the Ecosystem History of Biscayne Bay Web page.

FY 1998 Deliverables, Products Completed:

  • Ishman, S.E., Cronin, T.M., Brewster-Wingard, G.L., Willard, D.A., and Verardo, D.J., 1998. A record of ecosystem change, Manatee Bay, Barnes Sound, florida. Journal of Coastal Research, 26:125- 138.


Required Expertise:
 Trace Element

 Trace Element

Key Staff:

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