Biogeochemical processes controlling sedimentary phosphorus recycling in the Bay of Quinte

Session: Poster session

Maria Dittrich, University of Toronto Scarborough, [email protected]
Stefan Markovic, University of Toronto Scarborough, [email protected]
Jiying Li, University of Toronto Scarborough, [email protected]
Susan Watson, University of Waterloo, [email protected]
Shan Mugalingam, Lower Trent Conservation, [email protected]
Jay Guo, ECCC-ECCC Environment and Climate Change Canada, [email protected]
Andrew Morley, Ministry of the Environment, 1259 Gardiners Rd., [email protected]
George Arhonditsis, University of Toronto Scarborough, [email protected]

Abstract

Sediment phosphorus (P) recycling (internal loading) plays a major part in the nutrient dynamics of many eutrophic lakes and can delay the system’s response to nutrient management. Here, we quantified internal loading the Bay of Quinte (Ontario, Canada) and characterized biogeochemical processes that drive sediment P recycling.  Results showed that the dominant P binding forms in the surface sediments were potentially mobile redox-sensitive and metal oxide bound P in addition to more refractory calcium bound P. The pool of potentially mobile forms accounted for 63%-69% of the total P and sustained a diffusive reflux of 1-6.5 mg P/m²/day, emphasizing the prominent role of sediments in the ongoing eutrophication. Estimated rates of benthic organic carbon degradation indicate anaerobic mineralization as the main source of recycled P, despite the shallow depth (<15 m) and oxygenated water column. P-sorption on iron oxyhydroxides was the main process controlling seasonal P release, while elemental Fe:P ratios suggested a limited P binding capacity of surface sediments. This low sediment retention potential is indicative of a protracted “self-purification” that is likely to confound restoration efforts and should be factored into expectations for recovery.

1. Keyword
diagenesis

2. Keyword
phosphorus

3. Keyword
biogeochemistry