Mercury biomagnification in a Southern Ocean food web

José Seco*, Sara Aparício, Andrew S. Brierley, Paco Bustamante, Filipe R. Ceia, João P. Coelho, Richard A. Philips, Ryan A. Saunders, Sophie Fielding, Susan Gregory, Ricardo Matias, Miguel A. Pardal, Eduarda Pereira, Gabriele Stowasser, Geraint A. Tarling, José C. Xavier

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)
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Abstract

Biomagnification of mercury (Hg) in the Scotia Sea food web of the Southern Ocean was examined using the stable isotope ratios of nitrogen (δ15N) and carbon (δ13C) as proxies for trophic level and feeding habitat, respectively. Total Hg and stable isotopes were measured in samples of particulate organic matter (POM), zooplankton, squid, myctophid fish, notothenioid fish and seabird tissues collected in two years (austral summers 2007/08 and 2016/17). Overall, there was extensive overlap in δ13C values across taxonomic groups suggesting similarities in habitats, with the exception of the seabirds, which showed some differences, possibly due to the type of tissue analysed (feathers instead of muscle). δ15N showed increasing enrichment across groups in the order POM to zooplankton to squid to myctophid fish to notothenioid fish to seabirds. There were significant differences in δ15N and δ13C values among species within taxonomic groups, reflecting inter-specific variation in diet. Hg concentrations increased with trophic level, with the lowest values in POM (0.0005 ± 0.0002 μg g−1 dw) and highest values in seabirds (3.88 ± 2.41 μg g−1 in chicks of brown skuas Stercorarius antarcticus). Hg concentrations tended to be lower in 2016/17 than in 2007/08 for mid-trophic level species (squid and fish), but the opposite was found for top predators (i.e. seabirds), which had higher levels in the 2016/17 samples. This may reflect an interannual shift in the Scotia Sea marine food web, caused by the reduced availability of a key prey species, Antarctic krill Euphausia superba. In 2016/17, seabirds would have been forced to feed on higher trophic-level prey, such as myctophids, that have higher Hg burdens. These results suggest that changes in the food web are likely to affect the pathway of mercury to Southern Ocean top predators. Changes in foodweb dynamics influence Hg bioaccumulation in top predators.

Original languageEnglish
Article number116620
Number of pages11
JournalEnvironmental Pollution
Volume275
Early online date30 Jan 2021
DOIs
Publication statusPublished - 15 Apr 2021

Keywords

  • Antarctica
  • Contaminants
  • Polar
  • Stable isotopes
  • Trophic magnification slope

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