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geochemistry of florida bay sediments: i. nutrient history at five sites in eastern and central florida bay
Geochemistry of Florida Bay sediments: I. Nutrient history at five sites in eastern and central Florida Bay
W.H. Orem, C.W. Holmes, C. Kendall, H.E. Lerch, A.L. Bates, S.R. Silva, A. Boylan, M. Corum, M. Marot, and C. Hedgman
Abstract
Recent seagrass dieoff and massive microalgal blooms have focused attention on the health of the Florida Bay ecosystem. Changes in nutrient input and the nutrient dynamics of Florida Bay are hypothesized to be linked to these problems, but crucial baseline information is still lacking. Efforts to restore Florida Bay to its natural condition will require information on the nutrient history of the bay. The purpose of this study was to examine distributions of organic C, total N, and total P in carbonate sediments from sites of continuous and known sedimentation rate 210Pb and 137Cs dated, in eastern and central Florida Bay. These sediments provide a record of historical changes in the C, N, and P load to the eastern and central bay. Analyses were conducted on sediments from cores collected at five sites, and on buried seagrass fragments at two sites. At three of the sites, sediments from seagrass-covered and adjacent barren areas were examined to determine differences in sedimentary geochemistry. Stable isotope analyses ( Results were consistent with recent increases in N and P in eastern Florida Bay, beginning in the early to mid 1980's. The timing of the increase in nutrient load observed in the sediment data directly preceded the first observations of massive microalgal blooms and seagrass dieoff in Florida Bay in 1987. The observed nutrification was greater for P than N, and was most pronounced at the most northeasterly site sampled (Pass Key). Isotope data (
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U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 24 January, 2005 @ 10:04 AM (KP)