Mercury and selenium in wild mink (Neovison vison), evaluating concentrations molar ratio and associations with forestry intensity in Innlandet County Norway

Abstract

Mercury is a toxic heavy metal that is found to bioaccumulate and biomagnify in food webs across ecosystems. Monitoring of mercury and creating background levels for different areas is an important part of conservation and understanding possible drivers behind increased mercury concentrations and potential risk. Selenium is found to have the ability to alleviate the toxic effects of mercury and monitoring selenium and mercury together as well as their molar ratio, can assess the potential risk of negative effects from mercury. Here I assessed the concentration of selenium and mercury and the molar ratio between them in liver and fur samples in mink from Innlandet, Norway. Additionally, data that served as a proxy for forestry intensity, and the amount of forest and water in proximity to the capture site, was collected and generalized linear models and generalized additive models were fitted to explore the potential effects on mercury levels in mink. 56 mink were collected from the valleys Østerdalen, Glomdalen and Gudbrandsdalen between 2022 and 2024. The mean mercury across all valleys in liver was found to be 4.33 µg/g dw (SD ± 5.39) with a range 0.31 – 28.94µg/g dw. In fur samples, the mean was 19.02µg/g dw (SD ± 22.12) with a range of 1.57 µg/g dw 123.18 µg/g. No significant differences between area or sex were detected. For selenium, a significant difference between Østerdalen and Glomdalen was detected and the overall mean in the liver was 2.76 ± 1.08 µg/g dw with a range of 1.40 – 7.88 µg/g dw and fur had overall lower concentrations with a mean of 0.99 ± 0.37µg/g dw and a range of 0.55 µg/g dw– 2.33 µg/g dw. the mean hepatic molar ratio detected was 3.29 but showed a large range between 0.55 to 12.23. no significant results were found associated with the collected forestry or habitat for hepatic samples, for fur samples the amount of forest cover was a significant predictor though the model showed poor explanatory power. Most mink in Innlandet do not have mercury levels associated with negative health effects, but a substantial part of the population (up to 30 %) could have symptoms related to chronic mercury toxicosis, because of high mercury or low selenium concentrations. This study is therefore a contribution to reference levels of mercury in wild mink from Innlandet and proposes that future monitoring should include seasonal, dietary and environmental variables in future studies to possibly understand the large variability in mercury exposure found in mink from Innlandet.

Mercury is a toxic heavy metal that is found to bioaccumulate and biomagnify in food webs across ecosystems. Monitoring of mercury and creating background levels for different areas is an important part of conservation and understanding possible drivers behind increased mercury concentrations and potential risk. Selenium is found to have the ability to alleviate the toxic effects of mercury and monitoring selenium and mercury together as well as their molar ratio, can assess the potential risk of negative effects from mercury. Here I assessed the concentration of selenium and mercury and the molar ratio between them in liver and fur samples in mink from Innlandet, Norway. Additionally, data that served as a proxy for forestry intensity, and the amount of forest and water in proximity to the capture site, was collected and generalized linear models and generalized additive models were fitted to explore the potential effects on mercury levels in mink. 56 mink were collected from the valleys Østerdalen, Glomdalen and Gudbrandsdalen between 2022 and 2024. The mean mercury across all valleys in liver was found to be 4.33 µg/g dw (SD ± 5.39) with a range 0.31 – 28.94µg/g dw. In fur samples, the mean was 19.02µg/g dw (SD ± 22.12) with a range of 1.57 µg/g dw 123.18 µg/g. No significant differences between area or sex were detected. For selenium, a significant difference between Østerdalen and Glomdalen was detected and the overall mean in the liver was 2.76 ± 1.08 µg/g dw with a range of 1.40 – 7.88 µg/g dw and fur had overall lower concentrations with a mean of 0.99 ± 0.37µg/g dw and a range of 0.55 µg/g dw– 2.33 µg/g dw. the mean hepatic molar ratio detected was 3.29 but showed a large range between 0.55 to 12.23. no significant results were found associated with the collected forestry or habitat for hepatic samples, for fur samples the amount of forest cover was a significant predictor though the model showed poor explanatory power. Most mink in Innlandet do not have mercury levels associated with negative health effects, but a substantial part of the population (up to 30 %) could have symptoms related to chronic mercury toxicosis, because of high mercury or low selenium concentrations. This study is therefore a contribution to reference levels of mercury in wild mink from Innlandet and proposes that future monitoring should include seasonal, dietary and environmental variables in future studies to possibly understand the large variability in mercury exposure found in mink from Innlandet.