HOLOCENE ORGANIC SEDIMENT ACCUMULATION IN FLORIDA SPRING RUNS

Florida springs, like many freshwater systems, face three types of threats: reductions in water quantity, changes in water quality, and invasions of exotic species. As a result of these threats and perhaps other unidentified processes, many Florida springs have shifted from macrophyte to algal dominance. Several hypotheses have been suggested to explain this shift from macrophytes to algae in Florida springs, but none of these hypotheses seem to apply to all Florida springs that have experienced these shifts in dominant producers. One untested hypothesis suggests that muck accumulation in Florida spring runs provides a source of nutrients for the algae. We probed 14 Florida spring runs and measured the bottom sediments for organic layer depth. Preliminary results have thus far been obtained for 9 of the spring runs. Radiocarbon age estimates of organic macrofossils reveal that many of the springs began accumulating organic sediments several thousand years ago. While some of the bottom sediments are mineral-dominated with little organic material, many of the sampled springs contain abundant organic material (Loss on Ignition > 50%), even at great depth (>1m). Current work is focused on a detailed, multiproxy analysis of long sediment cores recovered from two of the spring runs, with the intent of investigating algal abundance and proliferation through the latter half of the Holocene at high resolution.