OA-29:

Seasonal change of surface layer bacterial community in Sendai Bay

Temporal and spatial dynamics of marine microbial community is actively studied with DNA-based analysis. However, there are only a few reports of microbial community in coastal area around Japan. In this study, to obtain fundamental knowledge of microbial community dynamics in Japanese coast, we monitored bacterial community in Sendai Bay (Tohoku area) by using monthly shotgun metagenomic data.
Seawater samples were collected from two sites in Sendai Bay, from 1m depth (surface) or from 10-50m depth (subsurface chlorophyll a maximum: SCM) of each site. Samples were collected approximately monthly from April 2012 to June 2013. Each sample was sequenced by use of ion PGM, and we used the sequence data from 40 samples. Each read was annotated based on NCBI-nr database, and then we compared the samples to assess the pattern of bacterial community.
The bacterial taxonomic composition greatly changed and showed strong seasonality. For example, the taxonomic composition of samples collected in Spring 2013 was very similar to those collected in Spring 2012, and the more seasonally distant samples tended to show the more different taxonomic composition, regardless of the sites and depth. On the other hand, functional gene composition based on SEED subsystem, which is to examine the potential function of the bacterial community, was rather stable.
It is consistent with previous studies in other localities that taxonomic composition showed strong seasonality and that functional gene composition was relatively stable. The dynamics of major taxonomic groups was also compared with previous reports. We also examine the relation between bacterial community and environmental condition such as inorganic nutrients in each season.

keywords:海洋メタゲノム,細菌群集