The Magnitude and Transformation of Resuspended Phosphorus in Western Lake Erie

Due to the history of eutrophication, there is potentially a large pool of phosphorus (P) in the sediment of Lake Erie that can be mixed into the water column by strong winds and currents. The magnitude and bioavailability of resuspended P, as well as its fate following resuspension, is poorly understood. To investigate this, we performed controlled resuspension experiments using sediment cores from three sites in Lake Erie’s western basin. We sampled water  for seven P fractions at four intensities of shear stress and found that the majority of resuspended P was in particulate forms that are less bioavailable. The highest shear stress measured would increase water column TP concentrations by 1.7-12.1 ug P/L depending on the site but only increase bioavailable P concentrations by 0.96-2.6 ug P/L. To examine the short-term fate of this material, we incubated resuspended sediment diluted into lake water for 48 hours while mixing. Concentrations of P forms were stable over 48 hours following resuspension, suggesting that sorption-desorption processes do not play a large role in changing net bioavailability of P. These findings are important for determining how sediment resuspension may affect quantity and bioavailability of P in western Lake Erie.

Primary Presenter: Connor Gluck, Cooperative Institute of Great Lakes Research (cgluck@umich.edu)

Authors:

Teige O'Brien, Cooperative Institute for Great Lakes Research  (teigeob@umich.edu)

Kelly McCabe, Cooperative Institute for Great Lakes Research  (mccabekm@umich.edu)