Lake Pavin History, geology, biogeochemistry, and sedimentology of a deep meromictic maar lake

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and Pradeep Ram 2005 ), likely through nutrient regeneration
that favors certain bacterial phyla ( alpha - and beta-
Proteobacteria ) over others ( Archaea and Bacteroidetes )
(Pradeep Ram and Sime-Ngando 2008 ). Such uneven and
heterogeneous impact of viral lytic activity for different pro-
karyotic phenotypes and/or genotypes probably is one of the
mechanisms by which viruses shape the host diversity and

community structure. We have demonstrated that this can

have a strong infl uence on the processes occurring in the

plankton food web dynamics (Pradeep Ram and Sime-

Ngando 2010 ).

A major pathway from which lytic viruses drive prokary-

otic community composition (PCC) is through their ultimate

dependence on the availability of specifi c host populations.

Fig. 14.7 Vertical variations of viral abundance ( VA ) and lytic produc-
tion ( VP ) ( a ), of bacterial abundance ( BA ) and production ( BP ) ( b ), of
the abundance of heterotrophic nanofl agellates ( HNF ) ( c ) and of the

contributions of viruses ( VBM ) and potential grazing from HNF to bac-

terial mortality ( D ) in Lake Pavin ( d ). Error bars represent standard

deviations for triplicates

T. Sime-Ngando et al.