CONSTANCY OF BACTERIAL ABUNDANCE IN SURFICIAL MARINE-SEDIMENTS

Controls on bacterial abundance in marine sediments remain poorly unde rstood despite the importance to biogeochemical processes, benthic eco logy, and in situ bioremediation. We report an analysis of direct micr oscopic counts of widely distributed surficial marine sediments, using a new approach of scaling abundance to the fluid volume of pore water within the sediments (bacteria FV-1). The analysis identified a great er constancy in benthic bacterial abundance than has been appreciated previously. Whether tested as a combined dataset or separately accordi ng to geographic region, less variance was observed when abundance was scaled to fluid volume rather than the traditional dimension of dry s ediment mass. The decrease in variance suggests that the primary contr ols on abundance, such as nutrient acquisition or predator encounter r ate, may also scale with porewater fluid volume. With values centered around 10(9) bacteria ml(-1) FV, regulation must differ fundamentally from the water column, where values average 10(5)-10(6) bacteria ml(-1 ) FV.