| Summary: | I analyzed bulk geochemical and biomarker data from subtropical lakes in Florida to determine how environmental change and anthropogenic effects are recorded in lacustrine sediments. On short (i.e. centennial) time scales, anthropogenic impacts are apparent in more recent sediments from three Florida lakes, and manifest themselves as increased algal lipid biomarker concentrations, more enriched delta13C values, and lower TOC:TN ratios. Across millennial time scales in Lake Harris, biomarker concentrations and their carbon isotopic values respond to regional hydrological changes in the early Holocene that were triggered by eustatic sea level rise. The carbon (delta13C) and hydrogen (deltaD) isotope ratios of lipid biomarkers extracted from a Lake Tulane sediment core serve as paleohydrology proxies across stadial/interstadial time scales during the late Pleistocene. Delta13C and deltaD lipid values of specific n-alkane chain lengths, demonstrate that subtropical Florida responded out of phase with high-latitude environmental changes during at least three of the late Pleistocene stadial-interstadial transitions. The region remained warm and wet, when the North Atlantic was cold and dry, because of oceanic/atmospheric patterns that limited northward export of warm, saline water. All three studies presented within, broadly agree with published literature on similar topics spanning identical timeframes. Thus, we are confident in the application of lacustrine biomarker data to measure regional change across highly variable time scales.
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