The article examines how climate change and warming Southern Ocean waters can increase the availability of mercury (Hg) in the Antarctic marine food web, due to the release of ice-stored Hg and higher methylation rates by microorganisms. The research focused on the biomagnification of Hg in the food web of the Antarctic Peninsula, one of the fastest warming regions in the world. Using stable isotopes of carbon (δ13C) and nitrogen (δ15N) to estimate feeding habitats and trophic levels, respectively, total Hg (T-Hg) concentrations were measured in various species, from Antarctic krill Euphausia superba to predators such as penguins, seabirds, and marine mammals (Figure 1).

The study measured stable isotope signatures and Hg concentrations in different species, including chinstrap penguins, skuas, gulls, southern giant petrels, and southern elephant seals. Significant differences in δ13C values among species were observed, with considerable overlap between seabird species and seals. Differences in δ15N values reflected variations in diet and trophic position. The lowest Hg concentrations were found in krill (0.007 ± 0.008 μg∙g–1) and the highest in southern giant petrels (12.090 ± 14.177 μg∙g–1).

Results showed a positive relationship between Hg concentrations and trophic levels, with Hg biomagnifying nearly twice at each trophic level. The study suggests that trophic interactions are the major pathways for Hg biomagnification in Southern Ocean ecosystems. The research also highlights that Hg concentrations may increase in marine organisms due to global warming, which enhances Hg methylation and its availability in low-oxygen waters. Long-lived, high trophic level predators, such as some seabirds and seals, are particularly vulnerable to the effects of Hg.

The study concludes that Hg biomagnification in the food webs of the Antarctic Peninsula results in high Hg burdens in top predators. As global temperatures rise, Hg concentrations are expected to increase, potentially causing significant negative effects on Antarctic organisms. The article emphasises the need for further studies to fully understand how taxonomic, geographic, and ecological differences influence Hg dynamics in the marine ecosystems of the Antarctic Peninsula.

Source: Matias, R. S., Guímaro, H. R., Bustamante, P., Seco, J., Chipev, N., Fragão, J., … & Xavier, J. C. (2022). Mercury biomagnification in an Antarctic food web of the Antarctic Peninsula. Environmental Pollution, 304, 119199.

DOI: 10.1016/j.envpol.2022.119199

Author: Laura Lopes