Effects of the frequency of water level fluctuations on fish mercury levels

Session: Chemical Contaminants (2)

Felicity Ni, University of Toronto Scarborough, [email protected]
George Arhonditsis, University of Toronto Scarborough, [email protected]
Satyendra Bhavsar, Ontario Ministry of Environment, Conservation and Parks, [email protected]
David Poirier, Ontario Ministry Of the Environment and Climate Change, [email protected]
Brian Branfireun, Western Univ., [email protected]

Abstract

In response to growing concerns over climate change, the Ontario energy budget is gradually shifting away from coal to one increasingly comprised of renewable resources. With this transition, hydroelectric energy has been explored as a viable alternative. However, among the concerns regarding hydroelectricity are the consequences of constructing impoundments which have been found to contain elevated levels of methylmercury (MeHg) and total mercury (THg) in both water and biota, as a result of a combination of physical and chemical processes. In this study, we simulated impoundment activity over four months at bi-daily, weekly, and monthly frequencies, with a control treatment of no fluctuations, to investigate the effects of water level fluctuations and sediment exposure on THg and MeHg concentrations in fish, water, and sediment. Our results indicated differences of MeHg and THg concentrations in sediment and water across the different treatments over the course of the experiment, supporting our hypothesis of an effect from fluctuation frequency on impoundments. We suggest that these trends are a result of physical fluctuations eliciting a pumping effect, whereby Hg is transferred between compartments. Our study offers insights into dam operational regimes and highlights the risks involved in impounding water systems.