Bacterial colonization of suspended solids in the River Danube

Abstract

The River Danube was studied in the vicinity of Vienna (Austria) to examine the Interactions among suspended matter, bacterial colonization and dissolved organic matter on a medium temporal and spatial scale. The concentration of suspended matter, the total number of particles and the number of bacteria attached to particles correlated with discharge rates. In the River Danube, 39% of the particles stained with Alcian Blue were colonized by bacteria, but only a small number of particles were heavily colonized. About 9.5% of the total bacterial community was found to b e associated with particles, abundance of free-living bacteria varied between 2.4 and 7.8 X 106 cells ml-' and attached bactenal abundance varied from 0.1 to 1.4 X 106 cells ml-l On average, 8 bacteria particle-' were found in the River Danube. Smaller particles were colonized more densely by bacteria than larger particles In the River Danube, 60 % of the particles were found to be in the size range of > 9 to 100 pm2 and 57 ' % of the attached bacteria colonized thls slze class.