Bering Sea | Ecosystem Perspectives
Mercury in Aleutian Island sea otter prey: Possible factor impeding population recovery? Presenter: Angela Gastaldi , argastaldi@alaska.edu, University of Alaska Fairbanks Paul Schuette , paul_schuette@fws.gov, U.S. Fish & Wildlife Service Todd O'Hara , tmohara@tamu.edu , Texas A&M University Caroline Cummings , caroline_cummings@fws.gov , U.S. Fish & Wildlife Service Lorrie Rea , ldrea@alaska.edu , University of Alaska - Fairbanks Mercury (Hg) is a global contaminant that bioaccumulates and biomagnifies through marine food webs with known toxicological effects at high concentrations. The central and western Aleutian Islands are a region with high concentrations of Hg in some Steller sea lions, a predatory marine mammal. Sea otter populations in Southwest (SW) Alaska, including the Aleutian Islands, have declined steeply since the 1990s. Here, we assess total Hg concentrations ([THg]) in potential SW Alaskan sea otter stock prey to determine if [THg] occurs at concentrations of interest or concern. We determined [THg] and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in 224 marine invertebrates from 8 islands across the western and central Aleutian Islands. The samples represented multiple feeding types, including: grazers (Cryptochiton stelleri and Strongylocentrotus sp.), a filter feeder (Mytilus sp.; mussels) and predatory sea stars (Leptasterias sp. and Evasterias sp.). [THg] were the lowest in the grazers, intermediate in the mussels, and highest in the predatory sea stars, as would be expected due to biomagnification. Some significant regional differences in [THg] for each group were noted, but differences were not consistent between species. For example, the highest [THg] in mussels were measured at Amchitka Island, while the highest [THg] for urchins were measured at Adak. Significant differences in δ13C and δ15N values occurred among islands for the grazers and mussels, but not predatory sea stars. Monomethylmercury concentrations ([MeHg+]) were measured for a subset of the samples from each group, and were strongly correlated with [THg] in mussels and sea stars. [MeHg+] in Strongylocentrotus sp. were very low and not significantly correlated with [THg].
Alaska Marine Science Symposium 2023 30 4
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