You are here:
Examining historical mercury sources in the St. Louis River estuary: How legacy contamination influences biological mercury levels in Great Lakes coastal regions
Citation:
Janssen, S., J. Hoffman, R. Lepak, D. Krabbenhoft, D. Walters, C. Eagles-Smith, G. Peterson, J. Ogorek, J. DeWild, A. Cotter, M. Pearson, M. Tate, R. Yeardley, AND M. Mills. Examining historical mercury sources in the St. Louis River estuary: How legacy contamination influences biological mercury levels in Great Lakes coastal regions. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 779:146284, (2021). https://doi.org/10.1016/j.scitotenv.2021.146284
Impact/Purpose:
Mercury is a common legacy contaminant addressed in sediment remediation projects as part of the Great Lakes Area of Concern program. However, it is unclear whether legacy-derived mercury still actively cycles within the food web and contributes to contemporary fish consumption advisories. To understand the relative contributions of legacy versus contemporary mercury sources in coastal zones we applied Hg, carbon, and nitrogen stable isotopes to the food webs of the St. Louis River Area of Concern and the Bad River, an analogous estuarine reference. Our results demonstrate that mercury derived from legacy contamination is still actively cycling within the Area of Concern food web, which directly influences the remedial and restoration strategies of this and other impaired Great Lakes coastal zones.
Description:
Industrial chemical contamination within coastal regions of the Great Lakes can pose serious risks to wetland habitat and offshore fisheries, often resulting in consumption thresholds that can directly impact human and wildlife health. Mercury (Hg) has been identified as a contaminant of concern in many of these highly urbanized and industrialized coastal regions, one of which is the St Louis River estuary (SLRE), the second largest tributary to Lake Superior. The SLRE has legacy contamination that has resulted in high Hg concentrations within sediments, but it is unclear whether legacy-derived Hg still actively cycles within the food web. To understand the relative contributions of legacy versus contemporary Hg sources in coastal zones we applied Hg, carbon, and nitrogen stable isotopes to the food webs of SLRE and the Bad River, an analogous estuarine reference. Hg stable isotope analysis showed that legacy contamination of Hg was widespread and heterogeneously distributed in sediments of SLRE, even in areas removed from known industrial Hg sources. The industrial Hg signal in sediments was also observed in benthic invertebrates, spiders, and prey fish from SLRE but was not noted in the Bad River. Direct comparison of prey fish between these regions confirmed that there was a distinct Hg source offset between the systems that was not attributable to natural ecological shifts. The isotopic Hg source to game fish was shown to be dependent on fish migration and feeding habits, with individuals feeding in Lake Superior likely accumulating Hg derived from atmospheric precipitation sources. These results suggest that Hg derived from legacy contamination within SLRE is still actively cycling within the food web, which can dramatically change the remedial and restoration strategies of other impaired Great Lakes coastal zones.
URLs/Downloads:
DOI: Examining historical mercury sources in the St. Louis River estuary: How legacy contamination influences biological mercury levels in Great Lakes coastal regions