Paleoecological investigations of recent lake acidification in northern Florida |
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| Authors: | P Roger Sweets Ray W Bienert Thomas L Crisman Michael W Binford |
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| Institution: | (1) Department of Geology, University of Minnesota, Duluth, MN, USA;(2) Present address: Department of Biology, Indiana University, 47405 Bloomington, IN, USA;(3) Department of Environmental Engineering Sciences, University of Florida, 32611 Gainesville, FL, USA;(4) Present address: Battelle Northwest, 98382 Seguim, WA, USA;(5) Florida State Museum, University of Florida, 32611 Gainesville, FL, USA;(6) Present address: Dept. of Landscape Architecture, Harvard University, 02138 Cambridge, MA, USA |
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| Abstract: | Thirty-two northern Florida lakes were analyzed to construct a transfer function relating surface sediment diatom assemblages to lakewater pH (R
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=0.89, s.e.=0.34). A paleoecological analysis of sediment cores from six of these lakes indicated that two have become more acidic in the last 50 years. The diatom inferred (DI) pH of L. Barco has declined between 0.56–0.82 in the 1900's and DI ANC (acid neutralizing capacity) by 28–46  eq l-1. The DI pH of nearby L. Suggs has declined 0.91 pH units and its DI ANC by 19 eq l-1. The timing of the inferred acidification is synchronous with known increases in emissions of sulfates and nitrates that are associated with acidic precipitation. Also, the increasing accumulation of substances related to emissions from the burning of fossil fuels (e.g., Pb, PAH) co-occurs with the lowering of DI pH in the sedimentary record. However, other processes may have accounted for or contributed to recent lake acidification. For instance, the drawdown of local water tables by human consumption may decrease the inseepage of ANC to seepage lakes. Such an effect would be synchronous with increasing depositions of sulfate. There is also clear evidence that Florida lakes are naturally acidic. Thus, paleoecological results indicate acidic deposition to be at certain contributor, but not necessarily the sole cause, of the recent further acidification of some naturally acidic Florida lakes.This is the tenth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D. F. Charles and D. R. Whitehead are guest editors for this series. |
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| Keywords: | acidic deposition diatoms hydrology Florida paleoecology sediment chemistry |
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