Figure F21. Depth distribution of total bacterial populations in sediment samples from Hole 1177A. The dashed line represents a general regression line of bacterial numbers vs. depth in deep-sea sediments (Parkes et al., 1994), with 95% upper and lower prediction limits shown by the lines of longer dashes. The shaded area on the left of the figure indicates where bacterial populations are too low to be detected with the acridine orange direct counts technique. The detection limit was 6 × 10⁴ cells/cm³ (any values within this area are constructed from sums of three enumerations and have no measure of error).