Anthony, James L.听1听;听Lewis, William听2
1听Department of Ecology and Evolutionary Biology, Cooperative Institute for AV名湿 in Environmental Sciences, University of Colorado
2听Department of Ecology and Evolutionary Biology, Cooperative Institute for AV名湿 in Environmental Sciences, University of Colorado
Nutrient mass balance studies suggest that phytoplankton production in lakes is subsidized by nutrients released from the sediments. Epilimnetic sediments, which directly underlie the lake鈥檚 mixed layer, are likely to be particularly important in this regard. However, previous studies examining fluxes of nutrients, particularly phosphorus, across the sediment-water interface (SWI) generally have ignored the influence of water-column turbulence. Through its influence on the diffusive boundary layer thickness at the SWI, turbulence is likely to mediate interfacial concentration gradients and facilitate P release despite an oxidized microzone at the sediment surface. To evaluate the role of epilimnetic sediments in lake P dynamics, we used oscillating grids to generate turbulence and regulate the thickness of the diffusive boundary layer at the sediment-water interface in intact sediment cores from Colorado lakes. Interfacial fluxes of P increased with increasing turbulence, but the net direction of P transfer depended on the concentration of phosphorus in the overlying water. Dissolved P concentrations in epilimnetic lake sediments and the epilimnetic water column appear to be in a dynamic equilibrium, with sediments acting to moderate extreme changes in water column P concentrations.