SS2.01 Effects of Biotic Interactions on the Structure and Function of Microbial Food Webs
Date: Wednesday, June 12, 2002
Time: 11:00:00 AM
Location: Saanich
 
BETTARELY, Université Clermont Fd II, Aubiere, France, Yvan.Bettarel@lbp.univ-bpclermont.fr
Sime-Ngando, T, , Université Clermont Fd II, , , 
Amblard, C, , Université Clermont Fd II, , , 
Carrias, J, F, Université Clermont Fd II, , , 
 
SIGNIFICANCE OF VIRUSES AND PHAGOTROPHIC PROTISTS FOR CONTROLLING BACTERIAL PRODUCTION IN TWO LAKES OF DIFFERENT TROPHY
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The seasonal and depth-related variability of the abundance of viruses, and the impact of viral lysis and protistan grazing (nanoflagellates and ciliates) on bacterial assemblages were investigated in the epi-, meta- and hypolimnion of two lakes of different trophy: the oligomesotrophic Lake Pavin and the eutrophic Lake Aydat, France. Mean viral abundance, viral production and burst size of infected bacteria were significantly higher in the most productive lake (i.e. Aydat), while mean potential infection rates (determined by examination of bacterial cellular contents by transmission electron microscopy) were, conversely, higher in the less-nutrient-rich lake (i.e. Pavin). Protistan predation (PP) and viral lysis (VL) controlled a greater fraction of bacterial production (BP) in Lake Pavin (VL = 14%, PP = 59%) than in Lake Aydat (VL = 9%, PP = 32%). In both lakes, BP was always less affected by protistan bacterivory and viral lysis in the epilimnion. Finally, the functional importance of viral lysis was apparently influenced by the trophic level of the waters, and the environmental conditions (e.g. solar radiations in the surface layers).