Studies on temporal changes in the sediment oxygen consumption and bacterial community structure in a seasonally hypoxic enclosed bay, Omura Bay

In order to clarify how bacterial community composition at surface sediment would change in a seasonally hypoxic enclosed bay (Omura Bay), diversity, richness and structure of the bacterial population were examined in the uppermost sediment layer (0-7 mm depth). Sediment samples and environmental parameters in the water column were collected in a center region of Omura Bay. From June through December in 2011, three replicate sediment cores were collected by scuba diving at each sampling from the center location at 20 ? 1 m depth with an acrylic pipe (31 cm long with 26 mm inner diameter), carefully avoiding the area with visible bioturbation. All core samples were kept at in situ temperature and carefully brought to the laboratory within 3 h after sampling, during which time samples were handled carefully to avoid direct exposure to sunlight and other physical disturbances. Sediment was extruded from cores down to 7 mm depth from the top. The top 0-7 mm layer of sediment was pooled and regarded as the uppermost sediment layer.