Investigations have been carried out on the bacterial diversity in the southern North Sea at a position called Tonne E3 where sediment originating from the Hamburg port area is dumped. An effect called tidal pumping causes the accumulation of sediment in the Port of Hamburg nowadays and gave occasion to the establishment of this dumping site in 2005. Bacteria react to changes in biotic and abiotic conditions very fast, e.g. due to high reproduction rates and the competence for gen transfer, which distinguishes them as qualified indicators for environmental impacts in general. Bacterial communities were investigated at the dumping site, a reference area and surrounding regions by genomic fingerprinting via Automated Ribosomal Intergenic Spacer Analysis (ARISA). This method focuses on the length polymorphism of the 16S-23S IGS in the bacterial genome thus providing estimates of bacterial diversity. Additionally sedimentary carbon and nitrogen contents were measured as they presumably affect bacterial abundances. It could be shown that in the immediate area of dumping a narrowing of the bacterial diversity had taken place compared to a reference area and surrounding regions. Carbon and nitrogen values were highly correlated with each other and positively correlated with the similarity among bacterial community patterns.