PARENT SESSION
Poster Session #23: Plankton.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Roles of resources and grazing in determining the composition of a bacterial community.

KAREL, IRENE^*,1, ¹ University of Kansas, Lawrence, KS

ABSTRACT- Manipulation of aquatic microcosms tested a heterogeneous model of trophic interactions against top-down and bottom-up models. Four replicate bacterial communities at each of four productivity levels received an inoculation of Colpidium striatum, a bacterivorous ciliate. Another four replicates at each productivity level served as an ungrazed control. Estimates of the density of C. striatum and each bacterial taxon present showed that grazing was a strong determinant of bacterial abundance and community composition, and productivity played a secondary role in mediating the effects of grazing. However, bacterial diversity was a result of the interaction between productivity and grazing, rather than a simple direct effect of either factor.

KEY WORDS: predation, bacteria, productivity , diversity