Pack-ice seals contribute to biological transfers of iron in the Southern Ocean

• Published in: Polar Biology
• Main Authors: Gilbert, Lola, Spitz, Jérôme, Jeanniard-Du-Dot, Tiphaine
• Other Authors: Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Observatoire pour la Conservation de la Mégafaune Marine (PELAGIS), LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: Biological iron vector; Antarctica; Sea ice; Primary productivity; Horizontal nutrient transfers; Vertical nutrient transfers; [SDE]Environmental Sciences; Antarctic; Southern Ocean; Weddell; Antarc*; Crabeater Seals; Polar Biology
• Online Access: https://hal.science/hal-04222350; https://hal.science/hal-04222350/document; https://hal.science/hal-04222350/file/Gilbertetal2023_PolarBiol_published.pdf; https://doi.org/10.1007/s00300-023-03198-6

International audience The contribution of animals to biological transfers of essential nutrients in ecosystems is increasingly recognised as a significant component of ecosystem functioning. In the Southern Ocean (SO), primary productivity is primarily limited by the availability of iron in the euphotic zone, which makes animals locally releasing iron-rich faeces potential fertilizers of the SO food web. We quantified the amounts of iron released by four species of Antarctic pack-ice seals using a bioenergetic model set up with best available data on species abundance, energetics, diets and prey composition. We estimated that leopard, crabeater, Weddell and Ross seals together release 208 tonnes of iron per year (95% confidence interval [104–378]). This is equivalent to the current contribution of SO humpback whales and four times that of SO sperm whales. At the population level, crabeater seals are the major contributors (73%), followed by Weddell (21%), leopard (4%) and Ross seals (1%). Locally, each species shows different daily individual iron release rates, suggesting the patchy and transient impact of these iron releases on primary producers might differ according to species. Beyond quantitative aspects, pack-ice seals’ contribution to horizontal, vertical and trophic transfers of iron depends on their habitat preferences, on their ecology and behaviours at sea and on the ice. Although their role as iron vectors has been mostly overlooked so far, our results place pack-ice seals alongside whales and penguins as significant components of the SO ecosystem biological iron cycling, thus contributing substantially to its productivity and functioning.