Giovannoni, S. J. Oregon State University,
Carlson, C. J. Bermuda Biological Station for Research,
Vergin, K. L. Oregon State University,

Establishing links between ecosystem scale processes and the activities of specific microbial populations is currently a major research challenge. Conceptual models provide compelling reasons to believe that the growth of specific microbial populations in planktonic ecosystems is linked to the amount and composition of dissolved organic carbon (DOC). However, the roles of individual species and the importance of seasonal and spatial distributions of microbial populations in DOC dynamics are not understood. Data emerging from molecular genetic studies of oceanic bacterioplankton are demonstrating that bacterioplankton communities are temporally and spatially ordered. Both in terms of the kinds of organisms present and their vertical distributions in the water column, generalities among temperate oceans are already apparent. Two of the most important observations are that picoplankon communities are dominated by ten major prokaryotic groups, only two of which contain cultivated members, and that the upper surface layer and lower surface layer differ dramatically in microbial community composition. Thus, the partitioning of resources by sympatric heterotrophic picoplankton belonging to the major picoplankon groups, and the partitioning of heterotrophic processes by different communities on the spatial scale of the surface layer, both need to be addressed. Presently the factors that control community composition are almost entirely unknown, but the amount and composition of DOC and inorganic nutrients, direct interactions among organisms, and physical contraints such as light and temperature, are obvious factors that may exert an effect on community composition. Hypothetical models are presented that explain microbial community composition in terms of DOC chemistry and inorganic nutrient availability.
Day: Tuesday, Feb. 2
Time: 08:30 - 09:00am
Location: Hilton of Santa Fe
Code: SS40TU0830H