Seasonal Depth-Related Gradients in Virioplankton: Standing Stock and Relationships with Microbial Communities in Lake Pavin (France) |
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Authors: | J Colombet M Charpin A Robin C Portelli C Amblard H M Cauchie T Sime-Ngando |
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Institution: | 1.LMGE, Laboratoire Microorganismes Génome & Environnement, UMR CNRS 6023,Université Blaise Pascal (Clermont-Ferrand II),Aubière Cedex,France;2.CRP-Gabriel Lippmann, Cellule de Recherche en Environnement et Biotechnologies,Luxembourg,Luxembourg |
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Abstract: | This study presents a depth-related survey of virioplankton abundance in Lake Pavin (Massif Central, France), in relation
to the abundances of heterotrophic prokaryotes, picocyanobacteria (Pcy), autotrophic picoeukaryotes (Peu), and of autotrophic
(ANF) and heterotrophic (HNF) nanoflagellates. The sampling strategy was designed to be representative of the physico-chemical
gradients of the whole water column of the lake, and the seasonal variability as well. In mixolimnic surface waters, all communities
were present and viral abundance peaked in summer and autumn. Viral abundance was significantly correlated (p < 0.001) with Pcy, Peu, and ANF, indicating that cyanophages and perhaps other phytoplankton viruses represent a significant
pool of viral standing stocks in the mixolimnion of Lake Pavin. Microautotrophs were absent in the deep monimolimnic water
masses, where viruses and heterotrophic prokaryotes exhibited highest seasonal abundances in summer and/or autumn and were
significantly correlated (p < 0.001) to each other. This indicates that the anoxic monimolimnion of Lake Pavin is an exclusive habitat for viruses and
heterotrophic prokaryotes. We conclude that in this habitat, host availability is prevalent over other factors (temperature,
oxygen, nutrients, grazers) in favoring viral proliferation. |
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