Foraging area rather than trophic level explains mercury concentration in Patagonian rockhopper penguin colonies

LOIS, NICOLÁS; BALZA, ULISES; DODINO, SAMANTA; POLITO, MICHAEL J.; PÜTZ, KLEMENS; BRASSO, REBECKA; RAYA REY, ANDREA

Virtual

Congreso; III World Seabird Conference; 2021

World Seabird Union

Mercury (Hg) is a widely available pollutant in the world's oceans. Its distribution is far from homogenous showing vertical stratification in the water column as well as spatial heterogeneity within and among ocean basins. In the Southern Ocean, penguins are considered effective indicators of Hg in the marine food web because of their relatively high trophic level, vagility combined with discrete and rather accessible reproductive grounds and their unusual feather molting pattern allowing for specific time-integrated sampling. Previous studies have shown elevated Hg concentrations in the South Western Atlantic Ocean. To provide further insights on regional variation in Hg prevalence within this basin we measured Hg concentration and carbon and nitrogen stable isotope composition in feathers of southern rockhopper penguins (Eudyptes chrysocome). Rockhopper penguins present population genetic structure in this area and different foraging areas for each genetic cluster. The northern genetic cluster forages at a higher trophic position, but yielded a two- to three-fold lower Hg concentration than the southern one. Interestingly, all adults from the southern cluster exceed the feather toxicity threshold of 5 μg/g. Previous studies also show that the Northern Patagonian Shelf presents lower concentrations compared to southernmost South America, which implies a recurring pattern rather than a particularity. This implies a different vulnerability due to the exposure to Hg for each cluster, but especially for predators feeding on rockhoppers, i.e. marine top predators, gulls and caracaras. Southern colonies could therefore serve as a model to investigate adverse effects of Hg contamination on penguins and downstream in their food webs.