SURVEY OF HEAVY METAL CONTENTS OF FISH IN A COASTAL LAKE MICHIGAN WATERSHED

Studies investigating the heavy metal/metalloid contaminants in fish have been performed for decades but are gaining interest while fish stocks are being stressed as food supplies, and as bioaccumulation pathways are better understood. Great Lakes fish studies have mostly focused on Hg, with lesser attention on other potential metal contaminants. There are also little data on fish from the individual drowned river mouths which supply the Great Lakes, particularly along the eastern shore of Lake Michigan. This abstract reports on the metal content of 2 commonly caught species (channel catfish and yellow perch) taken from a coastal lake (7.301 km2) in West Michigan. Approximately 85 fish were taken with pole and line methods from 6 different locations between July 2019 and July 2021. Samples of fish flank tissue were digested in acid and analyzed by ICP-OES techniques for contaminants including Antimony (Sb), Arsenic (As), Barium (Ba), Cadmium (Cd), Cerium (Ce), Chromium (Cr), Copper (Cu), Iron (Fe), Lead (Pb), Magnesium (Mg), Manganese (Mn), Nickel (Ni), Selenium (Se), and Zinc (Zn). Eight metals were detected at quantifiable levels, these were Ba, Cr, Cu, Fe, Mg, Mn, Se, and Zn. Tissue contents of Se and Cu are indistinguishable between sites. Preliminary results indicate that Mg concentrations are the highest for all the fish, occurring at the 1000 ppm level. Zn is the second highest concentration analyte present in the fish at ~20 ppm. Fe content of fish tissue is highly variable, ranging from 2 to 34 ppm. Se values average ~ 5 ppm. Mn occurs near or slightly less than 1 ppm and Cu contents are below 1 ppm. Cr is only quantifiable in ~ 34% of the fish analyzed and occurs at levels less than 1 ppm. Ba is detectable in ~20 % of the fish analyzed and is highly variable ranging from 0.1 to 5 ppm. The data show no statistical difference in metal contents between yellow perch and channel catfish, except for Cu, which is higher in catfish. Results were compared to some World Health Organization (WHO) guidelines. The average Zn, Fe, and Cu levels are below recommended levels. On average, Se and Cr levels in fish tissue are above WHO recommendations by approximately 2x to 5x. The explanation, implications, and potential significance of these findings are being investigated.