Eutrophication in Coote’s Paradise: Mechanisms and temporal dynamics of internal P loading
Chris Parsons, Fereidoun Rezanezhad, David O'Connell and Philippe Van Cappellen
Presented by Dr. Chris Parsons, Post Doctoral Fellow with the CERC Ecohydrology Research Group, University of Waterloo
Cultural eutrophication of aquatic environments is an extensive economic and ecological problem driven by excess phosphorus (P) loadings to waterways, either from current or historic anthropogenic activities. Excess P in surface water often accumulates in sedimentary pools which may be subjected to highly dynamic redox conditions, potentially resulting in later remobilization of P. We used controlled sediment suspension bioreactor experiments to simulate natural redox fluctuations occurring in nutrient rich sediment over time.
The results from both laboratory and field based experiments will be presented with respect to solid and aqueous phase P speciation and the mechanisms of P release from sedimentary pools. Particularly, the relative importance of phosphatase enzymes in controlling mobilization of P under different redox conditions and the interplay with the biogeochemical cycles of C, N, Fe, S and Si will be discussed.
Our results demonstrate that regular redox fluctuations may a) decrease long term phosphorus sequestration in the organic fraction of wetland and lacustrine sediments which has previously been shown to occur in static anoxic sediments; and b) increase internal loading of P by accelerating P release rates during short periods of anoxia.
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