Viral control of the bacterial community of a High Arctic glacier surface. ResoVir

Glacial ice surfaces comprise a seasonally-evolving three-dimensional photic zone which accumulates microbial biomass within the weathering crust, driving positive feedbacks in ice melt and modulating the flow of carbon to carbon-limited downstream ecosystems. Viruses appear influential on glacier bacterial communities; therefore we examined viral interactions with the bacterial communities eluted from the weathering crust of a Svalbard glacier. Estimation of viral decay rates that a strong viral control of bacterial productivity is mediated by a physically robust viral population. Amending microcosms with carbon and nutrients permitted the bacterial community to escape viral control, as evidenced by a decline in virus-to-bacterium ratio concomitant with increased cell numbers and productivity. Both the source bacterial community and microcosms were dominated by a few taxa, principally Janthinobacterium, seemingly challenging the “kill the winner” paradigm. We propose that a delicate interplay of bacterial and viral strategies affects biogeochemical cycling upon glaciers and, ultimately, downstream ecosystems.