Mercury biomagnification in an Antarctic food web of the Antarctic Peninsula.

Under the climate change context, warming Southern Ocean waters may allow mercury (Hg) to become more bioavailable to the Antarctic marine food web (i.e., ice-stored Hg release and higher methylation rates by microorganisms), whose biomagnification processes are poorly documented. Biomagnification of Hg in the food web of the Antarctic Peninsula, one of the world's fastest-warming regions, was examined using carbon (δ13C) and nitrogen (δ15N) stable isotope ratios for estimating feeding habitat and trophic levels, respectively. The stable isotope signatures and total Hg (T-Hg) concentrations were measured in Antarctic krill Euphausia superba and several Antarctic predator species, including seabirds (gentoo penguins Pygoscelis papua, chinstrap penguins Pygoscelis antarcticus, brown skuas Stercorarius antarcticus, kelp gulls Larus dominicanus, southern giant petrels Macronectes giganteus) and marine mammals (southern elephant seals Mirounga leonina). Significant differences in δ13C values among species were noted with a great overlap between seabird species and M. leonina. As expected, significant differences in δ15N values among species were found due to interspecific variations in diet-related to their trophic position within the marine food web. The lowest Hg concentrations were registered in E. superba (0.007 ± 0.008 µg g-1) and the highest values in M. giganteus (12.090 ± 14.177 µg g-1). Additionally, a significant positive relationship was found between Hg concentrations and trophic levels (reflected by δ15N values), biomagnifying nearly 2 times its concentrations at each level. Our results support that trophic interaction is the major pathway for Hg biomagnification in Southern Ocean ecosystems and warn about an increase in the effects of Hg on long-lived (and high trophic level) Antarctic predators under climate change in the future.

Microplastics and other anthropogenic particles in Antarctica: Using penguins as biological samplers.

Microplastics (< 5 mm in size) are known to be widespread in the marine environment but are still poorly studied in Polar Regions, particularly in the Antarctic. As penguins have a wide distribution around Antarctica, three congeneric species: Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarcticus) and gentoo penguins (Pygoscelis papua) were selected to evaluate the occurrence of microplastics across the Antarctic Peninsula and Scotia Sea. Scat samples (used as a proxy of ingestion), were collected from breeding colonies over seven seasons between 2006 and 2016. Antarctic krill (Euphausia superba), present in scat samples, contributed 85%, 66% and 54% of the diet in terms of frequency of occurrence to the diet of Adélie, gentoo and chinstrap penguins, respectively. Microplastics were found in 15%, 28% and 29% scats of Adélie, chinstrap and gentoo penguin respectively. A total of 92 particles were extracted from the scats (n = 317) and 32% (n = 29) were chemically identified via micro-Fourier Transform Infrared Spectroscopy (µ-FTIR). From all the particles extracted, 35% were identified as microplastics, particularly polyethylene (80%) and polyester (10%). It was not possible to ascertain the identification of the remaining 10% of samples. Other anthropogenic particles were identified in 55% of samples, identified as cellulose fibres. The results show a similar frequency of occurrence of particles across all colonies, suggesting there is no particular point source for microplastic pollution in the Scotia Sea. Additionally, no clear temporal variation in the number of microplastics in penguins was observed. Overall, this study reveals the presence of microplastics across Antarctica, in three penguin species and offers evidence of other anthropogenic particles in high numbers. Further research is needed to better understand the spatio-temporal dynamics, fate and effect of microplastics on these ecosystems, and improve plastic pollution policies in Antarctica.