Abstract
In this study, we aimed to reveal the temporal dynamics of microbial community respiration in the sediment of Omura Bay,Kyushu, Japan. Along with CTD profiling of the water column in the central basin of the bay from May through December 2011, we estimated the potential microbial community respiration by an in vivo electron transport system activity（ETSA）method. This method allowed us to estimate the whole oxygen consumption rate（WOCR）and chemical oxygen consumption rate（COCR）.WOCR and COCR increased from July through August, and a significant negative correlation was found between dissolved oxygen （DO）concentration in the bottom layer and WOCR during the period of bottom hypoxia（from July through September）（r＝－0．95, p＝0．05, n＝4）. It was further demonstrated that the WOCR correlated well with the amount of chlorophyll a integrated for the entire water column at the date of sediment sampling in the previous month（WOCR : r＝0．84, p＝0．07; COCR: r＝0．89, p＝0．04, n＝5）. These results strongly suggest that sediment oxygen consumption in central Omura Bay varied in response to the development of a hypoxic water mass in the bay, and that vertical flux of internal primary production in the water column fuels the sediment respiratory etabolism.
