BIVARIATE AND TRIVARIATE ANALYSIS IN FLOW-CYTOMETRY - PHYTOPLANKTON SIZE AND FLUORESCENCE

A curve-fitting method was used to characterize bivariate and trivariate flow cytometric data (cell volume, chlorophyll a fluorescence, phycoerythrin fluorescence) from a mixture of cultured algae and from natural populations of phytoplankton. The frequency distribution of cells in two or three dimensions was approximated by a sum of n bivariate or trivariate lognormal distributions, where n was the number of subpopulations in the assemblage. Each subpopulation was parameterized by the number of cells, the mean and standard deviation for each of the two or three variables, and a correlation coefficient for each pair of variables.