Cell density estimates of major functional groups are similar when measured by SFCM or microscopy.

<p>Estimates of cell density of four functional groups by SFCM and microscopy are moderately to strongly correlated on the log scale (r between 0.44 and 0.76, p<0.001 in all cases). Each point represents a single depth-specific sample measured using both methods. The black line is the 1:1 line and the red line represents the regression relationship (with confidence bands). In a small number of microscopy measurements, no cyanobacteria were found. These points are plotted with high transparency assuming that the true concentration was half the detection limit of 28 cells per mL. A small number of high-leverage points were excluded from the regressions, but the effect of this exclusion on slopes and correlation coefficients is modest. These excluded points can be identified in the plots because the regression lines do not extend to them.