Bacterial community structures associated with a natural spring phytoplankton bloom in the Yellow Sea, China

Bacterial community structures associated with a spring phytoplankton bloom were investigated using denaturing gradient gel electrophoresis (DGGE) and 16S rDNA clone libraries. Statistical and phylogenetic analyses applied on both molecular methods revealed differences in bacterial community composition between the bloom station and post-bloom station, as well as between two bloom stages (bloom- and decay-) at bloom station. At the class level, the bacterial community at the bloom station was dominated by Alphaproteobacteria, Flavobacteria and Gammaproteobacteria, whereas Alphaproteobacteria and Gammaproteobacteria were dominant at the post-bloom station. At order level, no obvious predominant subgroup was found at the post-bloom station. In contrast, predominant subgroups were observed in bloom samples and they changed over the course of bloom. Rhodobacterales (mainly Roseobacter) and Flavobacteriales (mainly Flavobacterium) were the predominant subgroups in the bloom period, whereas Roseobacter became the unique predominant subgroup in the decay-bloom period. Rhodobacterales and Flavobacteriales, which were dominant in the bloom-associated bacterial communities in the Yellow Sea, were also reported as dominant during bloom conditions in other ocean regions, suggesting that they play an important role in bloom events.