Eukaryotic diversity associated with the phycosphere of the seaweed Ulvaria obscura (Kützing) Gayral (Chlorophyta, Ulvophyceae) in the Svalbard Archipelago, Arctic region assessed using DNA metabarcoding

Microorganisms often occur in association with macroalgae, with the term “phycosphere” referring to the seaweed surface where they may be present. Phycosphere represents a poorly explored niche of marine diversity, especially in the polar regions. DNA metabarcoding provides a new and accessible method for the detection of DNA from different organisms, especially applicable for poorly known groups where taxonomic expertise is limited or unavailable. In this study we used DNA metabarcoding to provide an initial survey of eukaryotic communities associated with marine macroalgae obtained from the shores of Svalbard. Samples of Ulvaria obscura were sequenced and the DNA reads found were assigned to 75 taxa of six Kingdoms and 17 phyla: Chromista (Ciliophora, Haptophyta, Ochrophyta, Oomycota and Chrysophyta), Fungi (Ascomycota, Basidiomycota, Chytridiomycota, Mortierellomycota and Rozellomycota), Holozoa (Ichthyosporia), Metazoa (Cnidaria), Protozoa (Cercozoa, Discosea and Heterolobosea) and Viridiplantae (Bryophyta and Chlorophyta). The most abundant group was Viridiplantae, followed by Fungi. Our environmental DNA study confirmed that the phycosphere of U. obscura shelters a rich and complex microbiome, suggesting that Arctic macroalgae provide a hotspot of currently undescribed polar biodiversity. Additionally, our results were obtained during the first official Brazilian Arctic expedition, representing a historic step for the Brazilian Antarctic Program (PROANTAR).