Biofilm community structure in polluted rivers: abundance of dominant phylogenetic groups over a complete annual cycle.

The seasonal dynamics of river biofilm communities in two German rivers, the Elbe and one of its tributaries, the Spittelwasser, were investigated for the first time by using fluorescence in situ hybridization and a standardized biofilm sampling procedure. We show the importance of members of the beta subclass of the class Proteobacteria, which formed the largest single group in the massively polluted Spittelwasser at all times. Clear seasonal peaks of abundance were observed for the planctomycetes and the Cytophaga-Flavobacterium cluster.