Seasonal dynamics and diversity of Antarctic marine viruses reveal a novel viral seascape

Abstract

Abstract The Southern Ocean microbial ecosystem, with its pronounced seasonal shifts, is vulnerable to the impacts of climate change. Since viruses are key modulators of microbial abundance, diversity, and evolution, we need a better understanding of the effects of seasonality on the viruses in this region. Our comprehensive exploration of viral diversity in the Southern Ocean revealed a unique and largely uncharted viral landscape, of which 75% was previously unidentified in other oceanic areas. We uncovered novel viral taxa at high taxonomic ranks, expanding our understanding of crassphage, polinton-like virus, and virophage diversity. Our results indicate that Nucleocytoviricota viruses are an important and diverse group of Antarctic viruses, which regulate phytoplankton population dynamics. Our temporal analysis reveals complex seasonal patterns in viral populations, highlighting the interplay between bacteriophages, eukaryotic viruses, and their microbial hosts, whilst deepening our understanding of their roles in the world's most sensitive and rapidly changing ecosystem.