Seasonal shifts in the Marine Viruses of Goseong Bay, Korea.

Viruses are the most abundant biological entities in our oceans making up a sizeable proportion of genetic diversity in marine ecosystems. But considering this we know very little about their biodiversity and their role. In this study they look at the diversity of viruses found in Goseong Bay, as well as the effects of seasonal changes on the virus populations.

This study sampled sea water from 6 sites in Goseong Bay, Korea during each season of 2014. The study focused on how changes in temperature, salinity, dissolved oxygen and nutrient concentrations effected the biodiversity of viral populations. These variables were tested at the site when the sea water samples were taken. From this they found the only environmental variable that had a marked change with seasonality was temperature which ranged from as low as 8.95 °C in March to 26.4 °C in September. Once collected, the sea water samples were filtered and then sequenced using Illumina SBS sequencing. They then compared these results to a viral genomic sequence database. 

The results from this found there was 385,444 reads across all seasons with 77% of these being bacteriophages, 26% Algal viruses and 1% other viruses. The Pelagibacter phage was the most abundant making up 36% of this, but there was a total of 108 species present across the samples from all 4 seasons.

Regarding the 4 seasons, the authors found a clear difference between them, with viral abundance higher in March than in any other season. They also found that the dominant species changed with season with Pelagibacter phages dominating in September when it was hot and Roseobacter phages when it was cold in March.

 The four most common viruses identified overall were:

·         Pelagibacter ubique which feeds on dissolved organic carbon and nitrogen and can synthesize all amino acids.

·          Ostereococcus which infects algal plankton and is thought to shape communities by ‘killing the winner’.

·          Iridoviridae which infects invertebrates and vertebrates and is a lethal pathogen of fish. It has caused numerous economic losses across Asia due to the infection of aquaculture systems.

·         Poxvirus which infects marine mammals causing skin legions and may also cause disease in humans.

 These dominant viruses all have a clear impact on varying parts of the ecosystem, highlighting the positive but also the possibly damaging role viruses play in the marine environment. As well as this the presence/absence of certain viruses could act as indicators for risks to aquaculture and marine industry in this region.

Despite the clear importance of virus biodiversity there are very few studies about it. The authors suggest this is due to technical challenges generally based on limitations of resources. The authors also point out that even previous studies are not totally reliable, as although metagenomics is now well established, often the sample processing techniques are not and so can often leads to bias in the results.

 This study provides a useful foundation for future studies and for comparable analysis. As well as highlighting how, temperature can affect virus diversity which is more relevant than ever with the current threats from climate change.  The authors also suggest investigating the correlation between marine viruses and their hosts in future studies.

Paper reviewed

Hwang, J., Park, S., Park, M., Lee, S., & Lee, T. (2017). Seasonal Dynamics and Metagenomic Characterization of Marine Viruses in Goseong Bay, Korea. PLOS ONE, 12(1), e0169841. http://dx.doi.org/10.1371/journal.pone.0169841