Assessing mercury contamination in Southern Hemisphere marine ecosystems: The role of penguins as effective bioindicators

Mercury (Hg) is a global pollutant known for its significant bioaccumulation and biomagnification capabilities, posing a particular threat to marine environments. Seabirds have been recognized as effective bioindicators of marine pollution, and, among them, penguins present a unique opportunity to serve as a single taxonomic group (Sphenisciformes) for monitoring Hg across distinct marine ecosystems in the Southern Hemisphere. In this study, we conducted a comprehensive systematic review of Hg concentrations, and performed a meta-analysis that took into account the various sources of uncertainty associated with Hg contamination in penguins. Beyond intrinsic species-specific factors shaping Hg levels, our results showed that the penguin community effectively reflects spatial patterns of Hg bioavailability. We identified geographic Hg hotspots in Australia, the Indian Ocean, and Tierra del Fuego, as well as coldspots in Perú and the South Atlantic. Furthermore, specific penguin species, namely the Southern Rockhopper (Eudyptes chrysocome) and Macaroni penguin (Eudyptes chrysolophus), are highlighted as particularly vulnerable to the toxic effects of Hg. Additionally, we identified knowledge gaps in geographic areas such as the Galápagos Islands, South Africa, and the coast of Chile, as well as in species including Fiordland (Eudyptes pachyrhynchus), Snares (Eudyptes robustus), Erect-crested (Eudyptes sclateri), Royal (Eudyptes schlegeli), Yellow-eyed (Megadyptes antipodes), and Galápagos (Spheniscus mendiculus) penguins. Overall, our study contributes to the growing body of literature emphasizing the role of penguins as bioindicators of Hg pollution, but it also highlights areas where further research and data collection are needed for a more comprehensive understanding of Hg contamination in marine ecosystems in the Southern Hemisphere. [Display omitted] •Penguins are effective bioindicators of mercury.•Information is biased towards specific penguin species and marine regions.•Mercury hotspots in Australia, the Indian Ocean, and Tierra del Fuego.•Perú and the South Atlantic arise as mercury cold spots.•Further studies need to evaluate toxicity threshold in relation to Climate Change.