Survey of cyanotoxins and mercury contamination in Lake Champlain fish
From 2016-2017, the Lake Champlain Basin Program supported a study to measure cyanotoxins and mercury in the tissue of lake trout, walleye, smallmouth bass, yellow perch, and white perch fish from Lake Champlain. To analyze mercury concentrations, researchers collected ~600 fish; cyanotoxin concentrations were evaluated in 81 fish that were collected during high and low cyanobacteria bloom periods.
Cyanotoxins were below detection limits in all analyzed fish tissue samples. Water samples collected during cyanobacteria blooms also did not contain cyanotoxins at detectable levels.
Cyanotoxins were detected in the Lake in 2015 but were not detected in fish tissue in this study (2016-2017), suggesting that bioaccumulation did not occur.
Fish mercury concentrations were strongly influenced by fish length, species, and location collected.
Mercury concentrations were influenced by location, however, no consistent trend was observed for location among species.
All sampled fish species had specimens that exceeded the U.S. EPA mercury advisory limit (300 ppb) and all species except for yellow perch had at least one specimen that exceeded the U.S. FDA action limit (1000 ppb).
Walleye and smallmouth bass had higher numbers of specimens that exceed the USFDA action limit (38% and 17%, respectively) , suggesting that consumption of these species poses the greatest health risk.
Mercury concentrations in lake trout, walleye, and yellow perch have decreased significantly since initial mercury measurements in these species in 1987-1990.
Mercury concentrations in smallmouth bass and white perch did not decrease significantly since initial measurements were made in the mid-1990s, and were higher than the last survey of mercury in fish tissue in 2011.
Other takeaways and future work
More data are needed to determine the reason for the increase in mercury concentrations since 2011 in some species, and whether it is a trend that will continue. LCBP is supporting additional investigation into mercury concentrations in fish tissue, and the drivers behind mercury cycling and bioaccumulation. A future study will duplicate previous surveys of mercury in fish tissue in the lake to provide information on how mercury concentrations are changing. Samples will be collected in 2022 and 2023, and final results are expected in 2025.