Controls of phosphorus cycling in Lake Auburn, Maine, USA
Lake Auburn, Maine, serves as the major drinking water source to the cities of Lewiston and Auburn. It has historically had high water quality, as characterized by consistent low turbidity and a nonexistent or mild hypolimnetic anoxia; as a result, the water from the lake has been exempt from filtration by the EPA. In 2011 and 2012, however, summer epilimnetic phosphorus (P) concentrations increased significantly resulting in hypolimnetic dissolved oxygen loss and higher turbidity. A sustained increase in lake turbidity will compromise public health and eventually result in filtration requirement for water treatment at a great cost to the community. Excess P concentrations are brought about by (1) prolonged periods of hypolimnetic anoxia, partly caused by a warming temperature, and (2) the susceptibility of sediment P release that is controlled by P speciation. This project investigates P speciation in Lake Auburn sediment using sequential chemical extractions and 31P nuclear magnetic resonance (NMR) spectroscopy, and collects and analyzes the relevant species in the water column. These two data sets enable modeling of future behavior of Lake Auburn under various climate scenarios, and provide the basis for more generalized prediction of lake behavior in the northeastern U.S. This work supplements the existing knowledge of the lake, and its results will enhance lake and water supply management strategies.