Viral activity along a trophic gradient in continental margin sediments off central Chile

The influence of benthic viruses for bacterial mortality and carbon recycling was investigated in continental margin sediments off central Chile. Virus net production correlated significantly with the total benthic mineralization rate ( r(2) = 0.94, n = 5) across a coastal - shelf transect. Within anoxic bag incubations, viral production also correlated significantly with bacterial activity ( r(2) = 0.86, n = 7). The coupling between virus production and independent measurements of bacterial mineralization strongly suggested that benthic viral production was regulated by bacterial metabolic activity. From the rates of viral and bacterial production [ 2 - 6 x 10(6) virus-like particles ( VLP) cm(-3) h(-1) and 2 - 7 x 10(5) cells cm(-3) h(-1), respectively], the potential impact of viruses on bacterial mortality and dissolved organic carbon production was estimated. Viral-induced mortality corresponded to 44 - 138% of bacterial net production, indicating that viruses had substantial impact on bacterial mortality. The estimated release of viral lysates of 0.3 - 3.5 nmol C cm(-3) h(-1), however, contributed insignificantly to bacterial carbon respiration ( < 8%). Compiling data for various sediments using the same incubation approach confirmed that ( 1) viral activity is coupled to benthic mineralization rates, ( 2) virus-induced mortality constitutes a significant loss factor for benthic bacteria, whereas ( 3) viral-mediated recycling of organic carbon plays a minor role in benthic environments.