Marine benthic foraminifera diversity in extreme environments: A case study from the Edisto Bay (Ross Sea, Antarctica)

Antarctica and its coastal systems are highly sensitive to climate change, with rapidly evolving environmental conditions affecting benthic ecosystems. This study presents a detailed analysis of living benthic foraminiferal communities in Edisto Inlet (Ross Sea, Antarctica), a poorly explored coastal area. We investigated the spatial distribution of foraminiferal assemblages and their relationship with environmental variables, including sedimentation rate, redox potential, organic matter content, and bottom currents. By integrating foraminiferal, sedimentological, and oceanographic data, three distinct environmental zones were identified within the inlet, revealing pronounced ecological gradients: outer (station 180), middle (station 24), and inner (station 34). The outer zone exhibited high-energy conditions, well-oxygenated sediments, and diverse, abundant communities dominated by calcareous species Trifarina angulosa, monothalamous morphotypes Micrometula sp., and agglutinated taxa (Miliammina arenacea, Portatrochammina antarctica). The middle section, characterized by moderate sedimentation and suboxic conditions, supported lower diversity and abundance, with agglutinated species (Paratrochammina bartrami, Portatrochammina antarctica) and monothalamous taxa (Tinogullmia sp., Psammophaga magnetica) thriving in organic-rich sediments. The inner zone presented low-energy, highly hydrated sediments with strong microbial activity, a markedly reduced redox potential, and suboxic to anoxic conditions, where opportunistic calcareous (Globocassidulina biora, Globocassidulina subglobosa, Bolivinellina pseudopunctata) and monothalamous species (Psammosphaerid spp., Hippocrepinella hirudinea) persisted. Overall, our findings emphasize the strong link between benthic foraminiferal assemblages and local physico-chemical conditions, providing essential ecological baselines for Antarctic fjord systems. By demonstrating the responsiveness of living foraminifera to environmental variability, this study offers valuable insights into present ecosystem functioning and the implications of ongoing climate change for polar coastal environments.