Characteristics and Influence of Phosphorus Accumulated in the Bed Sediments of a Stream Located in an Agricultural Watershed

We investigated the accumulation and influence of bioavailable P (BAP) in sediments of a stream located in an agricultural area of the Lake Mendota watershed in Wisconsin, USA. During hydrologic events, the stream carried high concentrations of suspended sediment (up to 250 mg/l) and BAP (up to 2.5 mg/l). Bed sediments were highly enriched in BAP, as inventories of BAP in the top 10 cm of sediment ranged from 143 to 14,500 mu g P/cm(2). Space variations in BAP inventories were related to site-specific hydrodynamics and geochemical factors, including iron (Fe; r (2) = 0.71) and aluminum (Al; r (2) = 0.54) concentrations. Most sites behaved as potential sinks for dissolved reactive phosphate during hydrologic events and potential sources during base-flow periods. Through the combination of site-specific factors and geochemical controls, Dorn Creek modifies the amount, timing, and composition of P delivered from the watershed to downstream sites and water bodies.