BENTHIC PHOSPHORUS FLUXES IN THE LOWER GREAT MIAMI RIVER, SOUTHWEST OHIO

Human activities have increased loadings of nutrients to aquatic ecosystems during the past century. In late summer and early fall during low river flow, excessive concentrations of phosphorus (P) are present in the Lower Great Miami River (LGMR) and prevent it from being a high-quality river. Regulators have estimated that wastewater treatment plants are the main source of P during low river flow; however, riverbed sediment has not been examined as an additional potential source of P. We collected riverbed sediment and measured benthic P fluxes at eight representative locations along the LGMR during late summer and fall of 2015. Sediment and overlying water were incubated in a flux chamber, and total and filtered P were measured in the overlying water. Preliminary results indicate that P concentrations in overlying water increased during the incubations and that there is a net flux of P out of the sediment. These results suggest that benthic remobilization is an important source of P to the LGMR during low-flow conditions. Results from this study will contribute to a better understanding of P enrichment in the LGMR, and by extension, other comparable rivers impacted by both wastewater and non-point source inputs of nutrients.