Phosphorus retention and transformation in a dammed reservoir of the Thames River, Ontario: Impacts on phosphorus load and speciation

Extensive efforts are underway to reduce phosphorus (P) export from the Lake Erie watershed. On Canadian side, Thames River is largest tributary source of P Erie’s western basin. However, role dams in retaining and modifying riverine loading lake has not been comprehensively evaluated. We assessed whether Fanshawe Reservoir, dam reservoir on River, acts as a or sink P, using year-round discharge water chemistry data collected 2018 2019. also determined how in-reservoir processes alter speciation by comparing dissolved reactive total ratio (DRP:TP) upstream downstream loads. Annually, Reservoir was net for 25% (36 tonnes) 47% (91 TP 2019, respectively. Seasonally, oscillated between P. Net release occurred during spring summers driven internal hypolimnetic dam. The did exert strong influence DRP:TP annually, but increases both summers, concurrent with column stratification. Our analysis demonstrates that only an important modulates timing therefore propose potential existing reservoirs attenuate loads should be more thoroughly explored alongside based mitigation strategies.