AME 63:1-8 (2011)  -  DOI:

Viral abundance and activity in the deep sub-seafloor biosphere

Mathias Middelboe1,*, Ronnie N. Glud2,3,4, Manuela Filippini1,5

1Section for Marine Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
2Institute of Biology & Nordic Center for Earth Evolution (NordCee), Southern Danish University, 5230 Odense M, Denmark
3Greenland Climate Research Center (Co Greenland Institute of Natural Resources) Kivioq, Box 570, 3900 Nuuk, Greenland
4Scottish Association for Marine Science (SAMS), Dunstaffnage Marine Laboratory, Dunbeg, Oban, Argyll PA37 1QA, UK
5Present address: Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland

ABSTRACT: Subsurface abundance and distribution of viruses and prokaryotes was determined along a depth profile, down to 96 m below seafloor (96 mbsf), at Challenger Mound from the Porcubine Seabight (IODP Expedition 307). Viral and prokaryotic abundance decreased exponentially with sediment depth from 1.0 × 108 viruses cm–3 and 3.8 × 106 cells cm–3 at 4 mbsf to 4.9 × 106 viruses cm–3 and 9.8 × 105 cells cm–3 at 96 mbsf. The age of the sediment ranges from ca. 0.5 million yr before present (Ma) at 4 mbsf to ca. 2 Ma at 96 mbsf. Assuming that the decline in viral abundance with depth reflects a gradual decay of the viral assemblage over time, the estimated decay rate of the viral community is 1.2 × 10–6 ± 0.3 × 10–6 (SD) yr–1, corresponding to a half-life of the viral community of 5.8 × 105 yr. Measurements of viral and prokaryotic change in abundance were performed in incubations of undiluted, but homogenized, sediment samples (13.3 and 79.8 mbsf) in anaerobic bags. Viral abundance decreased rapidly (decay rates of 0.010 ± 0.002 [SD] and 0.022 ± 0.018 [SD] h–1, respectively) in the incubations, suggesting that homogenization exposed the viruses to degradation processes. We hypothesize that most of the deep subsurface viral communities inhabit a microenvironment where the viruses are protected against decay, and can therefore persist in undisturbed sediments for hundreds of thousands, perhaps even millions, of years.

KEY WORDS: Benthic viruses · Marine phages · Subsurface viruses · Viral decay · Sediment viruses · Viral ecology

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Cite this article as: Middelboe M, Glud RN, Filippini M (2011) Viral abundance and activity in the deep sub-seafloor biosphere. Aquat Microb Ecol 63:1-8.

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