Phytoplankton community structure in a Danubian backwater system: Response to environmental factors

摘要

Abiotic variables and phytoplankton composition were studied at an impounded part of the River Danube and at three backwaters upstream of Vienna. One of the backwaters was frequently connected to the Danube, whereas the other two sites were isolated with the exception of two flood events. Analysis of community stability revealed a pronounced change in the community structure at the flood pulses. The strongest impact was detected at the backwater that usually showed the highest differences to the main channel. Cluster analysis based on species abundance estimations resulted in a separation of the sites and detected similarities between the Danube and the permanently connected backwater. An Indicator Species Analysis was used to identify species indicative of the groups defined by the cluster analysis. A Detrended Canonical Correspondence Analysis was applied for examination of the relationship between the indicator species and the environmental factors. Connection and isolation, respectively, seemed to be important factors for the separation of sites and for the distribution of species. In times of isolation, seasonal variations of the environmental factors and, at one site, enhanced nutrient supply due to shallowness became determining factors.