Viral impacts on bacterial communities in Arctic cryoconite

The surfaces of glaciers are extreme ecosystems dominated by microbial communities. Viruses are found in abundance here, with a high frequency of bacteria displaying visible virus infection. In this study, viral and bacterial production was measured in Arctic cryoconite holes to address the control that viruses play in these highly truncated ecosystems. Mean bacterial carbon production in the sediments of cryoconite holes was found to be 57.8 ± 12.9 ng C g^-1 dry wt. h^-1, which predicted a mean of 1.89-5.41 × 10⁶ cells g^-1 dry wt. h^-1 based on a range of conversion factors. Relative to this, virus production was found to be high, up to 8.98 × 10⁷ virus like particles g^-1 dry wt. h^-1 were produced, which is comparable to virus production in sediments around the globe. The virus burst size was assessed by transmission electron microscopy and found to be amongst the lowest recorded in the literature (mean 2.4). Hence, to account for the measured virus production, the viral induced bacterial mortality was calculated to be more than capable of accounting for the mortality of all bacterial production. The data presented here, therefore, suggests that viral induced mortality is a dominant process for the release and recycling of carbon and nutrients in supraglacial ecosystems.