Drivers of interannual variability in virioplankton abundance at the coastal Western Antarctic Peninsula and the potential effects of climate change

An eight year time-series in the Western Antarctic Peninsula (WAP) with an approximately weekly sampling frequency was used to elucidate changes in virioplankton abundance and their drivers in this climatically-sensitive region. Virioplankton abundances at the coastal WAP show a pronounced seasonal cycle with interannual variability in the timing and magnitude of the summer maxima. Bacterioplankton abundance is the most influential driving factor of the virioplankton, and exhibit closely coupled dynamics. Sea ice cover and duration predetermine levels of phytoplankton stock and thus, influence virioplankton by dictating the substrates available to the bacterioplankton. However, variations in the composition of the phytoplankton community and particularly the prominence of Diatoms inferred from silicate drawdown, drive inter-annual differences in the magnitude of the virioplankton bloom; likely again mediated through changes in the bacterioplankton. Our findings suggest that future warming within the WAP will cause changes in sea ice that will influence viruses and their microbial hosts through changes in the timing, magnitude and composition of the phytoplankton bloom. Thus the flow of matter and energy through the viral shunt may be decreased with consequences for the Antarctic food web and element cycling.