Characterization of sedimentary P in Lake Erie and on-site quantification of algal available P stock

Session: Nutrient Sources, Transport, and Internal Cycling (2)

T.Q. Zhang, Agriculture and Agri-Food Canada, [email protected]
Y.T. Wang, [email protected], [email protected]
Yichen Zhao, University of Waterloo, [email protected]
Jan Ciborowski, Dept of Biological Sciences, Univ. of Windsor, [email protected]
Yingming Zhao, Ontario Ministry of Natural Resources, [email protected]
Ivan O'halloran , University of Guelph, [email protected]
Chin Tan, AAFC, [email protected]
Zhiming Qi, McGill University, [email protected]

Abstract

The recent resurgence of algal blooms in Lake Erie has sparked interest in determining availability of sedimentary phosphorus (P) for release into overlying water. Inorganic P (Pi) and organic P (Po) in Lake Erie sediments were characterized by sequential extractions in H2O, 0.5 M NaHCO3, 0.1 M NaOH, and 1.0 M HCl, respectively. While H2O-Pi, of which 38-67% was potentially available for release to water, was determined to be the most labile P fraction; it contributed relatively little to internal P loading. Relative to other P fractions, both NaHCO3-Po and NaOH-Po tended to become long-term sources for P release. Sedimentary P in the lake’s western basin may not release detectable P into the overlying water, whereas in the lake’s central and eastern basins it may contribute to internal P loads of 15.4 Gg P y-1 and 159 Mg P y-1, respectively.  Due to thermal stratification, water flow from west to east, and a large water volume in the central and eastern basins, internal P loads may not contribute to harmful algal blooms often observed in the western basin. These results help evaluate the efficacy of current P reduction conservation practices on the improvement of Lake Erie water quality.