Enumeration of sandy sediment bacteria: Are the counts quantitative or relative?

Several tests were carried out to enable evaluation of the precision with which sandy sediment bacteria could be enumerated. This represented the first attempt to place direct epifluorescence counts of benthic bacteria on a quantitative, rather than relative, ground. The tests combined in situ radioisotope ([H-3], [C-14]) labeling of sediment bacteria, bacterial dislodgment by ultrasonic treatment, and bacterial enumeration via fluorescent staining. The results provided direct and indirect evidence that the employed protocol for bacterial enumeration accounted for 88 to 98 % of all bacteria present in sediments. The identified approach thus allowed for a rather complete quantification of sediment bacteria. Since this protocol was more effective that the alternative techniques used in earlier studies, sediment bacteria may have been repeatedly undercounted in the past.