Bacterial composition and spatiotemporal variation in sediments of Jiaozhou Bay, China

Although coastal marine sediments harbor diverse bacteria with important ecological and environmental functions, a comprehensive view of their community characteristics is still lacking in typical environments along the China coast. We studied the diversity and composition of bacterial community in the sediment of Jiaozhou Bay and characterized their spatiotemporal patterns, aiming to analyze the effects of geographic heterogeneity, seasonal difference, anthropogenic activity, and eutrophication gradient on the bacterial ecology. Sixteen full-length bacterial 16S rRNA gene clone libraries were constructed from the sediment bacteria at four stations (A5, B2, D1, and D7) of Jiaozhou Bay over four seasons (February, May, August, and November). The bacterial diversity and community structure variation were analyzed. A total of 1088 16S rRNA gene sequences and 746 distinct operational taxonomic units (OTUs) (at 97 % sequence similarity level) were retrieved from the 16 clone libraries. Libraries of each sample revealed a high diversity, and a total of 17 bacterial phyla were identified. Bacteria lineages Proteobacteria (mostly gamma-Proteobacteria and delta-Proteobacteria), Actinobacteria, Bacteroidetes, and Planctomycetes, which are commonly found in marine sediments, were the dominant divisions in our samples. Meanwhile, some uncommon phyla, such as Deinococcus-Thermus and Lentisphaerae, were also detected. Distinct spatial patterns and noticeable seasonal variations of bacteria community were observed, indicating that environmental heterogeneity in spatial variation other than in temporal variation may be more important in determining the bacterial communities. Most of the abundant OTUs were related to sequences retrieved from the heavy-metal-polluted environments, indicating that the Jiaozhou Bay might be influenced by pollution. The bacterial communities in Jiaozhou Bay sediments are highly diverse. The four typical stations that we chose might experience different anthropogenic effects and eutrophication gradients, which shaped their bacterial community composition. The environment of Jiaozhou Bay may be under pressure exerted by multi-dimension anthropogenic activities. This study provided a novel insight into the bacterial community variations in Jiaozhou Bay, enriching knowledge about ecological bioindicators and mechanisms that maintain bacterial diversity and shape bacterial community composition.