title: Fish mercury levels appear to be increasing lately: a report from 40 years of monitoring in the province of Ontario, Canada.
abstract: Recent mercury levels and trends reported for North America suggest a mixed (positive/negative) outlook for the environmental mercury problem. Using one of the largest consistent monitoring data sets in the world, here we present long-term and recent mercury trends in Walleye, Northern Pike, and Lake Trout from the Province of Ontario, Canada, which contains about one-third of the world's fresh water and covers a wide geographical area (1.5 and 3 times larger than France and Germany, respectively). Overall, the results indicate that the fish mercury levels either declined (0.01-0.07 μg/g decade) or remained stable between the 1970s and 2012. The rates of mercury decline were substantially greater (mostly 0.05-0.31 μg/g decade) during the 1970s/80s possibly in response to reductions in mercury emissions. However, Walleye and Pike levels have generally increased (0.01-0.27 μg/g decade) in recent years (1995-2012), especially for northern Ontario (effect sizes for differences between the two periods ranged from 0.39 to 1.04). Proportions of Walleye and Pike locations showing a flat or increasing trend increased from 26-44% to 59-73% between the 1970s/80s and 1995-2012. Mercury emissions in North America have declined over the last few decades, and as such it is logical to expect recovery in fish mercury levels; however, other factors such as global emissions, climate change, invasive species, and local geochemistry are likely affecting the response time and magnitude.
authors.affiliation: Department of Physical and Environmental Sciences, University of Toronto , Toronto, Ontario, Canada M1C 1A4.
authors.forename: Nilima
authors.initials: N
authors.lastname: Gandhi
authors.forename: Rex W K
authors.initials: RW
authors.lastname: Tang
authors.forename: Satyendra P
authors.initials: SP
authors.lastname: Bhavsar
authors.forename: George B
authors.initials: GB
authors.lastname: Arhonditsis
mesh_terms: D000818:Animals; D004784:Environmental Monitoring; D017859:Esocidae / Q000378:metabolism; D005399:Fishes / Q000378:metabolism*; D060106:Lakes / Q000737:chemistry; D008628:Mercury / Q000032:analysis*; D008962:Models, Theoretical; D009864:Ontario; D010471:Perches / Q000378:metabolism; D013997:Time Factors; D014337:Trout / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury