The history of the ecosystem during the last 150-200 years is studied by analysis of faunal and floral assemblages from a series of shallow cores taken in Florida Bay. Cores are located at strategic sites in Florida Bay, with initial emphasis on the northeast and northern portions of the Bay where the most significant changes are thought to have occurred. These cores are submitted for Pb 210 analysis to determine the age and degree of disruption of the sediments. Cores that present a good stratigraphic record are sampled at closely spaced intervals for all macro-and micro-fauna and flora present. Quantitative down-core assemblage diagrams are drawn up and the various faunal and floral data are compared to look for correlated changes among the groups analyzed. Determinations of salinity, bottom conditions, nutrient supply and various other physical and chemical parameters of the environment are made for each sample based on the fauna and flora present. Data from all cores will be integrated to search for regional patterns of change in diversity and distribution of the fauna and flora, and data from Florida Bay will supplement and be correlated to onshore data and to Biscayne Bay (Ecosystems History: Terrestrial and Fresh Water Ecosystems of Southern Florida Project and Ecosystems History: Biscayne Bay and the southeast coast Project). The integrated data set will be analyzed to see if detected changes in biota correlate to alterations in physical parameters and/or historic records of human-induced modifications of the environment.
Our component of this study is to analyze the down-core faunal and floral assemblages, over the last 150-200 years. Cores are located at strategic sites in Florida Bay, with initial emphasis on the northeast and northern portions of the Bay where the most significant changes are thought to have occurred. These cores are submitted for Pb 210 analysis to determine the age and degree of disruption of the sediments. Cores that present a good stratigraphic record are sampled at closely spaced intervals for all macro- and micro-fauna and flora present. Quantitative down-core assemblage diagrams are drawn up and the various faunal and floral data are compared to look for correlated changes among the groups analyzed. Determinations of salinity, bottom conditions, nutrient supply and various other physical and chemical parameters of the environment are made for each sample based on the fauna and flora present. Data from all cores will be integrated to search for regional patterns of change in diversity and distribution of the fauna and flora, and data from Florida Bay will supplement and be correlated to onshore data and to Biscayne Bay. The integrated data set will be analyzed to see if detected changes in biota correlate to alterations in physical parameters and/or historic records of human-induced modifications of the environment.
2) Cores are a) visually examined, b) x-rayed, and c) Pb210 profiles are developed. These 3 methods determine if the sediments within the core are disrupted. If the core seems to be undisturbed, then processing proceeds.
3) Samples for sedimentologic, palynologic, charcoal, and isotopic analyses are removed.
4) Portions of the cores and the surface samples are washed through sieves down to 63 microns for calcareous samples.
5) Palynologic, and charcoal analyses proceed through a series of acidulation processes and slides prepared for counting of dinocysts, pollen grains, and charcoal.
6) Calcareous samples are dried and picked for mollusks, benthic foraminifera and ostracodes. Counts of taxa present are made.
7) Percent abundance diagrams are constructed. Core data is compared to modern analogue data for information on salinity and substrate preferences of species. Data from all faunal and floral groups are combined and analysis completed.
U.S. Department of the Interior, U.S. Geological Survey, Center for
Coastal Geology
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