Ecological risk of methylmercury to piscivorous fish of the Great Lakes region

Abstract

Contamination of fish populations with methylmercury is common in the region of the Laurentian Great Lakes as a result of atmospheric deposition and methylation of inorganic mercury. Using fish mercury monitoring data from natural resource agencies and information on tissue concentrations injurious to fish, we conducted a screening-level risk assessment of mercury to sexually mature female walleye (Sander vitreus), northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu), and largemouth bass (Micropterus salmoides) in the Great Lakes and in interior lakes, impoundments, and rivers of the Great Lakes region. The assessment included more than 43,000 measurements of mercury in fish from more than 2000 locations. Sexually mature female fish that exceeded threshold-effect tissue concentrations of 0.20 μg g(-1) wet weight in the whole body occurred at 8% (largemouth bass) to 43% (walleye) of sites. Fish at 3% to 18% of sites were at risk of injury and exceeded 0.30 μg g(-1) where an alteration in reproduction or survival is predicted to occur. Most fish at increased risk were from interior lakes and impoundments. In the Great Lakes, no sites had sexually mature fish that exceeded threshold-effect concentrations. Results of this screening-level assessment indicate that fish at a substantive number of locations within the Great Lakes region are potentially at risk from methylmercury contamination and would benefit from reduction in mercury concentrations.

Relating Fish Hg to Variations in Sediment Hg, Climate and Atmospheric Deposition

“…The co-varying influences on Fish THg are particularly strong for Sediment THg and ppt, likely due to direct and indirect precipitation-induced Hg inputs into lake water from the atmosphere and surrounding land. While these inputs would have the most direct and causative (2) and (5) imply that Fish THg to Sediment THg co-vary to some extent across Canada, this is not necessarily the case within region-specific studies with limited range in climatic variations as noted for northern Ontario [53] and for the Great lakes region [54].…”

Spatial Patterns in Wet and Dry Deposition of Atmospheric Mercury to Illinois Watersheds

“…Additionally, dry deposition studies of mercury to litterfall have shown that significant deposition to forested landscapes occurred with a magnitude similar or greater than wet deposition and accounted for 25 to 69% of total deposition (Risch et al, 2012b). Recent research shows that toxicological responses to Hg in fish and wildlife are occurring at significantly lower concentrations than previously reported (Dillon et al, 2010, Sandheinrich et al, 2012. Illinois currently has a state-wide fish consumption advisory for all fresh waters due to elevated methylmercury concentrations in fish taken from these waters.…”

Ratio of Mercury Concentration to PCB Concentration Varies with Sex of White Sucker (Catostomus commersonii)

“…The primary route of exposure of mercury to humans is via the consumption of fish [1][2][3][4]. Among the most serious threats to human health from mercury contamination is the impairment of normal brain development in the fetus [5][6][7][8][9][10][11]. Other toxic effects of mercury on humans include damage to the nervous system of adults, damage to the renal system, damage to the immune white sucker population.…”