Mercury temporal trends in top predator fish of the Laurentian Great Lakes

Abstract

Mercury (Hg) contamination is widespread in the Laurentian Great Lakes region and is a serious environmental concern. In anaerobic environments such as lake sediments, mercury is transformed into methylmercury (MeHg) and can biomagnify up the food chain to toxic concentrations. The Great Lakes Fish Monitoring Program (GLFMP), administered by the US EPA Great Lakes National Program Office (GLNPO), aims to monitor temporal trends of mercury in the five Great Lakes using top predator fish as biomonitors. Total Hg (THg) concentrations were measured in Great Lake fish collected between 1999 and 2009. Single factor ANOVA determined that average fish THg concentrations over this time period in the five lakes were significantly different from one another in the order of Superior > Huron > Michigan > Ontario > Erie. By fitting the data to three different models (linear, quadratic, and two-segment piecewise), it was determined that Hg concentrations in top predator fish (lake trout, or walleye in Lake Erie) are currently increasing in Lake Erie and the Apostle Island sampling site in Lake Superior. Significant decreasing trends are evident in Lakes Michigan, Ontario, and the Rockport sampling site in Lake Huron, although all of the lakes exhibit elevated concentrations in fish compared to historic concentrations. As new Hg emission controls are implemented in the US, continued monitoring of Hg in Great Lakes fish will be needed to determine if they influence the current concentrations and trends.

Mercury in the Great Lakes region: bioaccumulation, spatiotemporal patterns, ecological risks, and policy

“…In the Great Lakes, a similar increasing trend has been seen in two studies of Lake Erie walleye (1999( -2009( , Zananski et al 20111977, Bhavsar et al 2010. In general, however, mercury concentrations in Lake Erie fish appear to be lower than those from other Great Lakes, with average concentrations highest in fish from Lake Superior.…”

“…Feather mercury concentrations in nestlings declined by nearly 80% from 1989 to 2010, a trend attributed to a lake-level stabilization order by the International Joint Commission that was implemented in 1999. Interestingly, as observed in some fish populations (Monson 2009;Monson et al 2011;Bhavsar et al 2011;Zananski et al 2011), there appears to be a biphasic response in nestling mercury concentrations with increasing concentrations observed over the period spanning 2000-2010.…”

“…First, mercury concentrations in fish from the Great Lakes proper are significantly lower than in inland lakes and reservoirs in the region Zananski et al 2011). Second, concentrations of mercury in biota are related to, and can be predicted from, environmental conditions in aquatic systems that are known to influence ecosystem sensitivity to mercury.…”

“…In general, however, mercury concentrations in Lake Erie fish appear to be lower than those from other Great Lakes, with average concentrations highest in fish from Lake Superior. Zananski et al (2011) examined mercury in predatory fish from the Great Lakes with linear, quadratic, and two-segment piecewise regression models, and observed that mercury levels in lake trout from Lake Ontario, such as U.S. and Ontario largemouth bass , have significantly declined (4% per year from 1999 to 2009). During this period, mercury in predatory fish from Lake Michigan also declined, while concentrations in fish from sites in Lake Huron decreased or exhibited no significant trend.…”

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“…chironomid larvae), zooplankton, and even its own eggs (Stefanovic 1948;Naumovski 1995). As a top predator fish, the salmonid are more prone to pollutant bioaccumulation, resulting in associated biological effects (Savini et al, 2010;Zananski et al, 2011). Data are very rare or not available on the types/levels of pollutants close to the urban centers, the major sources of contaminants, nor the -cleanest‖ areas of Lake Ohrid.…”