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

Abstract

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 (r²=0.94, n = 5) across a coastal–shelf transect. Within anoxic bag incubations, viral production also correlated significantly with bacterial activity (r²=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 [2–6×10⁶ virus-like particles (VLP) cm⁻³ h⁻¹ and 2–7×10⁵ 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.

Keywords:

• Bacterial mortality
• benthic mineralization
• spatial variation
• viriobenthos
• virus production

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgments

We wish to thank Professor Victor Ariel Gallardo, Dr Javier Sellanes and Sergio Contreras, University of Concepción for invaluable help during our stay in Dichato. Anni Glud is acknowledged for excellent technical assistance and Kai Finster for running the sulphate reduction analyses. The study was supported by the Danish Natural Sciences Research Council. Three anonymous reviewers and subject editor Antje Boetius provided valuable suggestions that improved the manuscript.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark