Mercury Concentrations in Sentinel Fish Exposed to Contaminated Sediments Under a Natural Recovery Strategy Within the St. Lawrence River Area of Concern at Cornwall, Ontario, Canada.

Legacy mercury (Hg) sediment deposits are a long-term issue within the St. Lawrence River (Cornwall) area of concern with three depositional areas along the Cornwall, ON waterfront containing sediments that exceed the Ontario Sediment Quality Guidelines for Hg. Assessing the bioavailability of these Hg-contaminated sediments plays a crucial role in evaluating the effectiveness of the Cornwall Sediment Strategy based on a natural recovery approach. We collected specimens of fallfish (Semotilus corporalis), round goby (Neogobius melanostomus), and yellow perch (Perca flavescens) to assess spatial and temporal trends of Hg concentrations in various areas along the Cornwall waterfront, including zones of contaminated sediments and non-contaminated reference sites. This study revealed that (1) Hg concentrations in fish collected from the contaminated zones remain greater than those of fish from non-impacted locations, indicating that natural recovery is not yet achieved, (2) total Hg concentrations in yellow perch collected in 2016 were greater than those obtained during a previous assessment, indicating a reversal of the previously observed long-term declines, and (3) total Hg concentrations in yellow perch collected at the outlet of Gray's Creek compared with yellow perch from contaminated zones, suggesting other important inputs of Hg to the ecosystem than the legacy contaminated sediments.