title: Can mercury in fish be reduced by water level management? Evaluating the effects of water level fluctuation on mercury accumulation in yellow perch (Perca flavescens).
abstract: Mercury (Hg) contamination of fisheries is a major concern for resource managers of many temperate lakes. Anthropogenic Hg contamination is largely derived from atmospheric deposition within a lake's watershed, but its incorporation into the food web is facilitated by bacterial activity in sediments. Temporal variation in Hg content of fish (young-of-year yellow perch) in the regulated lakes of the Rainy-Namakan complex (on the border of the United States and Canada) has been linked to water level (WL) fluctuations, presumably through variation in sediment inundation. As a result, Hg contamination of fish has been linked to international regulations of WL fluctuation. Here we assess the relationship between WL fluctuations and fish Hg content using a 10-year dataset covering six lakes. Within-year WL rise did not appear in strongly supported models of fish Hg, but year-to-year variation in maximum water levels (∆maxWL) was positively associated with fish Hg content. This WL effect varied in magnitude among lakes: In Crane Lake, a 1 m increase in ∆maxWL from the previous year was associated with a 108 ng increase in fish Hg content (per gram wet weight), while the same WL change in Kabetogama was associated with only a 5 ng increase in fish Hg content. In half the lakes sampled here, effect sizes could not be distinguished from zero. Given the persistent and wide-ranging extent of Hg contamination and the large number of regulated waterways, future research is needed to identify the conditions in which WL fluctuations influence fish Hg content.
authors.affiliation: U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, USA, jhlarson@usgs.gov.
authors.forename: James H
authors.initials: JH
authors.lastname: Larson
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Maki
authors.forename: Brent C
authors.initials: BC
authors.lastname: Knights
authors.forename: Brian R
authors.initials: BR
authors.lastname: Gray
mesh_terms: D000818:Animals; D002170:Canada; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry; D060106:Lakes / Q000737:chemistry; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis; D010471:Perches; D014481:United States; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury