Spatial dynamics of rotifers in a large lowland river, the Elbe, Germany: How important are retentive shoreline habitats for the plankton community?

The longitudinal dynamics of Rotifers in the Potamal region of the River Elbe between Dresden, km 46, and Geesthacht, km 583, was investigated on a Lagrangian survey in 2000 which included transversal sampling (left bank, main channel, right bank) and sampling of five major tributaries and backwaters to evaluate lateral impacts on the zooplankton community. A simple model of longitudinal development for the dominant species Trichocerca pusilla was calculated, based on the results of an in situ incubation in Dresden and on literature data and compared with the dynamics observed on the Lagrangian survey. To characterize the influence of groyne fields on the main channel zooplankton community, an additional lateral sampling was conducted in August 2000 at Havelberg, km 423. Zooplankton community was clearly dominated by rotifers. A distinct downstream-directed increase of rotifers was observed. Longitudinal development of rotifers could be explained predominantly by reproduction during downstream transport.