SEDIMENT SOURCE SHAPES INTERACTIONS BETWEEN DISSOLVED AND PARTICULATE PHOSPHORUS DURING HIGH FLOW EVENTS IN AN AGRICULTURAL WATERSHED

Eutrophication of freshwater ecosystems is a global environmental problem often caused by excess bioavailable phosphorus (P). Thus, it is important to understand the sources and sinks of bioavailable P in a watershed. Previous work suggests that during high-flow events, which dominate annual P and sediment loads, exchange of P between dissolved and particulate forms affects the bioavailability of P exports to recipient ecosystems. Yet, suspended sediment is derived from many sources on the landscape, which can differ in composition and likely, affinity for P sorption. Because human activities can affect sediment source, it is important to understand how source influences sediment-P (sedP)-dissolved P (DP) interactions during high flow. To address this, we collected seven distinct sources (four streambank soils, two cropland soils, and streambed sediment) from a Maumee River tributary, the Maumee watershed being the main source of P fueling Lake Erie cyanobacteria blooms. Using source material collected in May, June, and December, we conducted three experiments which examined sedP-DP interactions in a simulated high-flow environment for 120 hours. Streambed and streambank sources sorbed P, with most P sorption occurring during the first day, while cropland soils did not absorb additional P. Our results indicate that sediment source likely influences sedP-DP interactions during high flows, suggesting that changes in land management that alter the relative balances of sediment sources may influence in-stream P transformations and bioavailability of P to recipient ecosystems.

Primary Presenter: Morgan Shaw, The Ohio State University (shaw.759@buckeyemail.osu.edu)

Authors:

Morgan Shaw, Aquatic Ecology Laboratory, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Columbus, Ohio, USA  (shaw.759@buckeyemail.osu.edu)

Amanda Schmidt, Department of Geosciences, Oberlin College, Oberlin OH USA  (aschmidt@oberlin.edu)

Tanja Williamson, U.S. Geological Survey, Ohio-Kentucky-Indiana Water Science Center, Louisville, KY, USA  (tnwillia@usgs.gov)

James Hood, Aquatic Ecology Laboratory, Department of Evolution, Ecology, and Organismal Biology, The Ohio State University, Columbus, Ohio, USA; Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio, USA  (hood.211@osu.edu)