W9 AM Biomonitoring
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 339-340

(FRE-1117-825149) Spatial and Temporal Trends in Tissue Mercury Burdens in Ontario Fish Populations over a 27-Year Period (1976-2003).

French, T.D.¹, Campbell, L.M.¹, Mierle, G.², Scheider, W.³, Hayton, A.³, ¹ Queen's University, Department of Biology and School of Environmental Studies, Kingston, ON, Canada² Ontario Ministry of Environment, Dorset Environmental Research Centre, Dorset, ON, Canada³ Ontario Ministry of Environment, Biomonitoring, Environmental Monitoring & Reporting Branch, Etobicoke, ON, Canada

ABSTRACT- Tissue mercury (Hg) concentrations in many fish species, particularly those in higher trophic levels, are elevated in lakes and rivers across Ontario, Canada. It is widely believed that Hg burdens in fish first started to rise at the time of the Second World War, and that they reached a maximum during the late 1960s and early 1970s. While Hg burdens in fish have reportedly been declining since the mid-1970s, burdens in many species still often exceed Health Canada guidelines for human consumption. The Ontario Ministry of Environment (OME) has been collecting data on fish tissue Hg burdens in lakes and rivers across Ontario since the mid-1970s to the present. It is estimated that 165,000 - 170,000 individual fish, from 86 species and 1,600+ sites, have been tested for Hg, with this equating to about 1.5 million database records. While the OME uses these data primarily for the production of the biennial Guide to Eating Ontario Sportfish and for the identification of Hg sources, we have used the long-term database to quantify how species-specific Hg burdens have changed over time in select lakes and rivers across Ontario in relation to changes in environmental exposures to Hg. Limnological data (morphometry, trophic status, substrate characteristics, flushing rates, thermal and oxygen dynamics) were used to determine whether there are particular features of lakes and rivers that make them especially susceptible to Hg accumulation or, conversely, comparatively resistant to Hg accumulation. Our research provides estimations of the time it will take for Hg burdens in Ontario sportfish populations to decline to levels acceptable for regular human consumption.

Key words: Mercury, Pollution, Ontario, Contaminants