PRELIMINARY LATE HOLOCENE DIATOM PALEOECOLOGY OF LAKE JACKSON, FLORIDA/ALABAMA

Despite some evidence of hydroclimate variability from terrestrial indicators, few long paleoecological records of limnobiotic response from lakes in the southeastern US exist. Here we present preliminary results from the fossil diatom record of Lake Jackson, a sinkhole lake located on the border of Florida and Alabama. Diatoms are extremely sensitive to changes in the lake environment, including changes in water chemistry and lake level, and readily preserve in lake sediments. We analyzed a set of 76 diatom samples over the 6.7-meter (~4000-year) lake record. Our initial results suggest that the sediments from the core site were dominated by diatom taxa typically indicative of shallow, acidic water conditions throughout most of the Late Holocene. These species primarily belong to the following genera: Pinnularia, Frustulia, and Neidium. The more recent record shows a decrease in total diatom abundance and some changes in the dominant species, but without substantial changes in the dominant genera. Although these results suggests limited sensitivity to lake-level fluctuations, we compared changes in total diatom productivity, frustule preservation, and down-core changes between diatom genera from fossil diatom assemblages to a panel of multiple proxies. Taken together, these records can provide important context for the long-term hydroclimate variability and the paleoecological responses to drought in this region.