High-resolution description of insular and fjordic benthic food webs along the West Antarctic Peninsula

The West Antarctic Peninsula (WAP) is one of the most rapidly warming region on Earth. In this context, it is crucial to improve our understanding of the consequences of future changes in the local biotic and abiotic environments on marine ecosystem functioning. Here, we focused on food web structure of shallow-water benthic communities. In February 2023, the TANGO1 expedition, using a sailboat, brought nine Belgian scientists to the WAP. To assess the importance of environmental changes on local food web dynamics, five benthic communities were investigated, focusing on macroalgae forests (n=2) and sedimentary soft bottoms (n=3). These stations were distributed between two contrasted environments, Dodman Island (Grandidier Channel, 66°S) & Blaiklock Island (Bigourdan Fjord, 67.5°S). These two locations differed markedly in terms of sea-ice cover, and in terms of general hydrography (small island exposed to the Grandidier Channel’s currents VS fjord system surrounded by active glaciers). At each station, basal food sources (i.e. sediment-associated POM, water-column POM, macroalgae, microphytobenthos) as well as benthic invertebrates (435 individuals, 64 morphospecies) were sampled quantitatively to assess their biomass, and for later stable isotope analysis. Using stable isotope ratios of carbon, nitrogen and sulphur, and Bayesian tools, we aim to formally represent the communities in isotopic space, and to compare their topologies along the environmental
gradient studied. These representations will then be used to test whether differences in food web structure reflect general community characteristics, such as the higher biomass of organisms measured in macroalgae forests, which also display the greatest species diversity.