Bering Sea | Fishes and Fish Habitats MASTER’S POSTER PRESENTATION
Carbon and nitrogen stable isotopes of amino acids reveal the influence of trophic level and primary production sources on mercury concentrations in fishes from the Aleutian Islands, Alaska
Presenter: Michelle Trifari , mtrifari@alaska.edu, University of Alaska Fairbanks Matthew Wooller , mjwooller@alaska.edu, University of Alaska Fairbanks Lorrie Rea , ldrea@alaska.edu, University of Alaska - Fairbanks Todd O’Hara , tmohara@tamu.edu, Texas A&M University Gretchen L. Lescord , glescord@wcs.org, Wildlife Conservation Society (WCS) Canada Andrew C. Parnell , Andrew.Parnell@mu.ie, Maynooth University Benjamin Barst , bdbarst@alaska.edu, University of Alaska Fairbanks
Total mercury concentrations exceed thresholds of concern in some Steller sea lion ( Eumetopias jubatus ) tissues from certain parts of the Aleutian Islands, Alaska. To better understand why, we examined the trophic ecology and mercury concentrations of fishes (n = 474 total) that are part of Steller sea lion diets. Compound-specific stable carbon isotopes (expressed as δ13C values) in essential amino acids and nitrogen isotopes (expressed as δ15N values) in amino acids in muscle tissue were used to quantify the proportional contributions of primary production sources and trophic positions of these fish. Previous total mercury analyses, coupled with additional monomethylmercury analyses of a subset of fish muscle samples, substantiated previous findings that fishes from the west of Amchitka Pass, a discrete oceanographic boundary of the Aleutian Archipelago, have higher muscle total mercury concentrations relative to fishes from east of the pass. All fish muscle samples were analyzed separately for both stable carbon and nitrogen isotopes of amino acids. The δ13C values of essential amino acids in fish muscle demonstrated that although most fishes obtained their essential amino acids primarily from algae, some species varied in the extent to which they relied on this primary production source. Certain δ15N values of amino acids of the same fish samples indicated that trophic positions of fishes were higher from the west relative to the east of the pass for some species. Total mercury concentration was positively correlated with bulk δ15N values, δ15N values of glutamic acid, and trophic positions. However, only trophic magnification slopes using δ15N values of glutamic acid indicated a higher rate of mercury biomagnification to the west of Amchitka Pass. Multiple linear regression models revealed that trophic position was the most important driver of fish muscle total mercury with a smaller amount of variation explained by other parameters such as proportional contributions of primary production sources, fish condition, and catch location. Collectively, these results indicate that elevated trophic positions and rates of total mercury biomagnification are potential determinants of the higher fish total mercury concentrations to the west of Amchitka Pass and a possible contributing factor to the noted total mercury observations in Steller sea lions.
Alaska Marine Science Symposium 2023 215
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