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When microbiologists first applied the tools of their trade to the oceans of the world, they quickly learned that water samples contained variable numbers of bacteria, depending on sample location and the method of measurement. Estuarine water samples were routinely found to contain greater numbers of culturable bacteria than coastal ocean water samples, which, in turn, contained greater numbers than samples from the abyssal ocean. In general, microscopic counts always exceeded culture medium counts, for any given sample, and activity measurements often suggested a greater bacterial presence than indicated by the culture counts. Claude ZoBell was one of the first marine microbiologists to make such observations (ZoBell and Upham, 1944), and over the years many other investigators repeated and expanded these findings. Typical were the observations of Grimes et al., (1984) who reported that acridine orange direct counts (AODCs) of bacteria in seawater samples usually exceeded plate counts on heterotrophic plating media by four to six orders of magnitude, and they discussed reasons for the discrepancy. Data analysis presented by Meyer-Reil (1978) also supported these observations, further indicating the common failure of cultural-count data and direct-count data to exhibit any correlation. Illustrative of this discrepancy is the data presented in Figure 1.