Biodiversity and Trophic Structure of the Rocky Intertidal Macroinvertebrate Assemblages in Southern Patagonia, Argentina

ABSTRACT The objective of this study was to characterise the intertidal macroinvertebrate assemblages from marine and estuarine macrotidal rocky shores in Southern Patagonia, Argentina. To achieve this aim, we analysed spatial changes in biodiversity and trophic structure, and explored their relationship with the main physical environmental variables. The study was conducted during spring 2021 and summer, autumn and winter 2022 in the south of Santa Cruz province, at sites with different salinity regimes and wave exposure. Different tidal levels and substrate slopes were compared. Data of abundance, richness and diversity of taxa and functional feeding groups were analysed and compared using univariate and multivariate statistics. Distinct macroinvertebrate assemblages could be recognised in the rocky intertidal of the study area, which were related to the different combinations of environmental variables. The salinity regime was the environmental factor most closely associated with the changes in the composition and diversity of the macroinvertebrate assemblage at a medium geographic scale. The macrotidal regime that characterises the region together with the particular geomorphology of its rocky shores highlights the effect of those variables that cause stress due to desiccation and exposure to extreme conditions. The main physical factors determining the diversity of taxa and feeding strategies at a small geographical scale are tidal level and substrate slope. Protection from waves favours the settlement of infaunal species and exotic species in sheltered rocky shores, where they find a more suitable and less stressful environment for their settlement. The results obtained are important for their biogeographic and ecological implications and provide relevant information for establishing management and conservation measures for coastal environments.