Mercury biomagnification in a Southern Ocean food web

Biomagnification of mercury (Hg) in the Scotia Sea food web Southern Ocean was examined using stable isotope ratios nitrogen (?15N) and carbon (?13C) as proxies for trophic level feeding habitat, respectively. Total Hg isotopes were measured samples particulate organic matter (POM), zooplankton, squid, myctophid fish, notothenioid fish seabird tissues collected two years (austral summers 2007/08 2016/17). Overall, there extensive overlap ?13C values across taxonomic groups suggesting similarities habitats, with exception seabirds, which showed some differences, possibly due to type tissue analysed (feathers instead muscle). ?15N increasing enrichment order POM zooplankton squid seabirds. There significant differences among species within groups, reflecting inter-specific variation diet. concentrations increased level, lowest (0.0005 ± 0.0002 ?g g?1 dw) highest seabirds (3.88 2.41 chicks brown skuas Stercorarius antarcticus). tended be lower 2016/17 than mid-trophic (squid fish), but opposite found top predators (i.e. seabirds), had higher levels samples. This may reflect an interannual shift marine web, caused by reduced availability a key prey species, Antarctic krill Euphausia superba. In 2016/17, would have been forced feed on trophic-level prey, such myctophids, that burdens. These results suggest changes are likely affect pathway predators.