Diversity and spatial distribution patterns of shallow benthic assemblages in Admiralty Bay, South Shetland Islands

Antarctic marine environments are undergoing rapid changes due to climate changes, with glacial retreat leading to increased ice impact and sediment runoff. This study used photographic sampling to assess the structure and diversity of shallow-water (0-30 m) benthic assemblages in Admiralty Bay, King George Island. The aim was to identify the factors influencing these patterns and to provide baseline data for evaluating potential impacts of ongoing climate change. Diversity varied by location, with the central basin exhibiting the highest species richness (S' = 9.55 ± 2.63 SD) whereas areas around Dufayel Island showed the highest diversity (H' = 1.52 ± 0.45 SD). Species richness and diversity increased with depth, peaking at 30 m, where community structure became more homogenous (J' = 0.769 ± 0.09 SD). Substrate type had a significant effect on these communities, with hard bottoms supporting greater richness and diversity. Multivariate analysis revealed that depth and location were key factors shaping community structure (R = 0.615, p = 0.001; R = 0.537, p = 0.001). Our study shows that depth is a key factor influencing benthic assemblage composition and structure in Admiralty Bay, primarily by buffering against physical disturbances such as waves and ice impact. Substrate type and proximity to glaciers, along with associated sedimentation rates, also play important roles in shaping community distribution and composition. These findings provide essential baseline data on Antarctic benthic communities in Admiralty Bay, while also highlighting their vulnerability to climate-driven changes and offering a framework for monitoring ecosystem responses to future glacial retreat.