Mercury biomagnification in a Southern Ocean food web

• Published in: Environmental Pollution
• Main Authors: Seco, José, Aparício, Sara, Brierley, Andrew, Bustamante, Paco, Ceia, Filipe, Coelho, João, Philips, Richard, Saunders, Ryan, Fielding, Sophie, Gregory, Susan, Matias, Ricardo, Pardal, Miguel, Pereira, Eduarda, Stowasser, Gabriele, Tarling, Geraint, Xavier, José
• Other Authors: CESAM & Department of Chemistry, Universidade de Aveiro, Pelagic Ecology Research Group, Scottish Oceans Institut, Faculdade de Ciências e Tecnologia = School of Science & Technology (FCT NOVA), Universidade Nova de Lisboa = NOVA University Lisbon (NOVA), LIttoral ENvironnement et Sociétés - UMR 7266 (LIENSs), Institut national des sciences de l'Univers (INSU - CNRS)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Marine and Environmental Sciences Centre (MARE UC), Universidade de Coimbra Coimbra, Centre for Environmental and Marine Studies Aveiro (CESAM), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Government of South Georgia and the South Sandwich Islands, Centre for Functional ecology, University of Coimbra Portugal (UC), Centro de Estudos do Ambiante e do Mar (CESAM)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: Trophic magnification slope; Stable isotopes; Contaminants; Antarctica; Polar; [SDV.TOX.ECO]Life Sciences [q-bio]/Toxicology/Ecotoxicology; Antarctic; Austral; Scotia Sea; Southern Ocean; Antarc*; Antarctic Krill; antarcticus; Euphausia superba; Stercorarius antarcticus
• Online Access: https://hal.science/hal-03489570; https://hal.science/hal-03489570/document; https://hal.science/hal-03489570/file/Seco%20et%20al%202021%20ENPO.pdf; https://doi.org/10.1016/j.envpol.2021.116620

International audience Biomagnification of mercury (Hg) in the Scotia Sea food web of the Southern Ocean was examined using the stable isotope ratios of nitrogen (d15N) and carbon (d13C) 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 d13C 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). d15N 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 d15N and d13C 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 mg g-1 dw) and highest values in seabirds (3.88 ± 2.41 mg 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.