The Potential of Organic Sediments in Florida Spring Runs as Records of Environmental Change.

The origin of modern spring flow in Florida is generally presumed to correspond with sea-level stabilization at or near present levels during the Middle Holocene. Low sea level and associated karstic aquifer drawdown have been assumed to have prevented artesian flow in current Florida spring systems throughout the Terminal Pleistocene. However, little paleoenvironmental work has been undertaken to test these assumptions. Substantial ecological changes within many of Florida's spring runs over the past two decades have raised interest in the use of sediment core analyses to characterize the nature, extent, timing, and potential triggers of these changes. We evaluated the extent and age of organic material accumulation in a broad sample of fifteen spring runs in central Florida. Radiocarbon dating of sediment cores indicated that many of these runs have accumulated organic material for thousands of years; five of the fifteen spring runs contain organic material that pre-dates Holocene sea-level stabilization. Therefore, either saturation or inundation of Florida's artesian spring runs was much more geographically and temporally variable than has been previously assumed. It is likely that paleoenviron-mental reconstructions of those runs with lengthy sediment records will produce new knowledge about paleoclimate, paleobiology, and more recent ecological change. [ABSTRACT FROM AUTHOR]