| Newnans Lake is a hypereutrophic lake 10 km east of Gainesville. It drains an area dominated by low impact land uses (plantation forests, state owned lands) and yet exhibits among the worst water quality in North Florida, principally expressed as a extreme concentration of phosphorus. This work, which started in 2006 and has been ongoing, first sought to understand the source of the nutrients (principally nitrogen and phosphorus) and now is focused on refining elemental budgets for the watershed. The principal finding was that most of the P was of geologic origin, and that management activities intended to improve water quality need to focus on the mobilization of P from the Hawthorn Group, a P rich geological formation that underlies the entire Northern Highlands ecoregion of Florida and beyond. In addition to understanding the source of P enrichment, its impacts on N enrichment in the lake, and the sources of water (i.e., there is no evidence for groundwater inputs to the lake), we have recently started to explore the role of sediment diffusion in the mass balance for the lake, particularly since the surface sediments are massively enriched in soluble P. |
