Patagonian fjords/channels vs. open ocean: phytoplankton molecular diversity in Southern Chilean coast

Environmental filtering hypothesis studies have revealed immense diversity of microorganisms across oceans; however, these studies are scarce along the Southeast Pacific coast. In this work, we describe the molecular diversity of phytoplankton communities from two biogeographic areas with contrasting oceanographic characteristics, namely fjords and channels versus the open Pacific Ocean (36°S to 53°S). Both areas have seen an increase in the frequency and intensity of Harmful Algal Bloom events (HABs). Using a molecular approach based on metabarcoding of the SSU ribosomal gene, we retrieve micro-phytoplankton diversity, community composition, and biogeographical patterns. The ASVs assigned to Dinophyceae and Bacillariophyta classes show differences in richness and dominance between both studied areas. The diversity pattern described in this work shows a higher harmful potential in fjord/channel areas versus the open ocean, which provides grounds for future studies about the factors triggering temporal variations in phytoplankton communities within these two contrasting environments.