Viruses and phage impact upon the health of environments in unexpected ways. For example, they are important drivers of genetic diversity, they have been implicated in the acceleration of the biological carbon pump and their activity underpins the (re-)cycling of nutrients that support healthy marine ecosystems. However, there are very few studies of viral diversity for the Australian marine environments.
We carried out the first study of the genetic diversity of viral communities within the East Australian Current system and the adjacent Tasman Sea, two critical oceanographic systems that have a dramatic influence on the regional climatology of South-Eastern Australia. We analysed 60 metagenomes obtained from 24 different locations, that vary by sample depth and by fractionation method (0.2um, < 0.2um). Using both VirSorter1 and bespoke analysis pipelines, we identified more than 20,000 viral contigs ranging from 2kbp to 190kbp, including more than 80 complete circular viral genomes, with the predominate group in the EAC genetically related to cyanophage. Preliminary analyses of viral diversity reveals four distinct groups, geographically clustered by surface water mass and depth. There was a clear distinction between the viral communities in the surface of the EAC and the colder Tasman Sea. This work provides an important baseline to support research to unravel the dynamics of microbial communities in a complex ocean system.