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.