Mercury Concentrations, Habitat and Trophic Position of Antimora rostrata and Macrourus holotrachys from South Georgia (Southern Ocean)

Mercury (Hg) is considered a neurotoxin capable of severely harming wildlife, including marine ecosystems. It has a high dispersal capacity through atmospheric and oceanic currents, allowing it to reach remote regions across the globe, such as the Southern Ocean, where it accumulates in marine food webs. Despite its ecological relevance, little was known about Hg concentrations in deep-sea fishes from this region.

In this study, researchers analysed two deep-sea fish species from South Georgia: Antimora rostrata (blue antimora), a more pelagic species, and Macrourus holotrachys (bigeye grenadier), a demersal species. In 2020, individuals were collected and four tissues (muscle, brain, liver and gills) were analysed, along with stable isotopes, to determine the habitat and trophic position of each species.

The results showed that:

  • Muscle was the tissue with the highest mercury concentrations in both species.
  • A. rostrata consistently showed lower concentrations than M. holotrachys.
  • Only in M. holotrachys did Hg concentrations increase with body length and weight, suggesting bioaccumulation throughout life
  • Differences also reflected habitat use, since the demersal species (M. holotrachys) is more closely associated with benthic food webs, which are generally richer in Hg.
  • A. rostrata occupies a lower trophic level than M. holotrachys.

Unexpectedly, the brain showed high Hg concentrations, raising questions about potential neurotoxic effects in these fishes and their predators.

These results reveal that different feeding strategies and habitats shape contaminant accumulation in deep-sea species, with implications for ecosystem health and for top predators that depend on them.

Figure 1: Mercury concentrations (Mean ± 1 SD, µg g-1 dw) in different tissues (Muscle, Brain, Liver and Gills) of Antimora rostrata and Macrourus holotrachys. Different lowercase (for Antimora rostrata) and uppercase (for Macrourus holotrachys) letters above bars indicate significant differences among tissues in each species (Friedman test with Nemenyi post hoc test, p < 0.05). * between bars indicate differences between the same tissue in both species (Mann-Whitney test, p < 0.0001).
Figure 2: δ13C and δ15N values in the muscle of Antimora rostrata (n = 23) and Macrourus holotrachys (n = 22) from South Georgia. Mean ± standard deviation.

Source: Vaz, D. B., Queirós, J. P., Xavier, J. C., Bustamante, P., Abreu, J., Pereira, E., Hollyman, P. R., Coelho, J. P. & Seco, J. (2025). Mercury Concentrations, Habitat and Trophic Position of Antimora Rostrata and Macrourus Holotrachys from South Georgia (Southern Ocean). Marine Pollution Bulletin. DOI:10.2139/ssrn.5360416

Author: Diana

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