SS2.01 Effects of Biotic Interactions on the Structure and Function of Microbial Food Webs
Date: Wednesday, June 12, 2002
Time: 9:30:00 AM
Location: Saanich
 
PernthalerJ, Max-Planck-Institute for Marine Microbiology, Bremen, Germany, jperntha@mpi-bremen.de
 
Mortality and the structure of bacterioplankton communities
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The biomass size distributions of bacterioplankton communities and the limited ranges of total cell numbers are frequently taken as evidence that pelagic bacteria are exposed to high and size-selective mortality. There are at least two hypotheses which cause of mortality (viral lysis or predation) most strongly affects microbial community structure. However, field evidence for either view is poor. Although a number of studies have focussed on individual aspects, there is little synoptic information about co-occuring changes of the population sizes of bacterial phylotypes, of species-specific growth and mortality rates, and of predator and viral community structure. I shall argue that the data required to, e.g., decide between the two above hypothesis in parts cannot even be produced by present-day techniques. Moreover, since it is still considered avant-garde to address functional properties of individual bacterioplankton populations at all, we know almost nothing about the effects of food web structure on the in situ growth and activities of different pelagic bacterial species.