PRIMARY PRODUCTION OF PROCHLOROPHYTES, CYANOBACTERIA, AND EUKARYOTIC ULTRAPHYTOPLANKTON - MEASUREMENTS FROM FLOW CYTOMETRIC SORTING

A partitioning of ultraphytoplankton primary production among prochlorophytes, cyanobacteria, and eucaryotic algae was made by shipboard flow cytometric sorting of C-14-labeled cells. Aggregate primary production was derived from the sum, over all three ultraplankton groups, of the product of cell abundance and cell-specific rate of C-14 uptake which ranged from 0.03 to 4 fg C cell-1 h-1 for prochlorophytes and 0.2 to 10 fg C cell-1 h-1 for cyanobacteria. Results indicated that the dominant primary producer was not necessarily the numerical dominant nor necessarily the group with the highest cell-specific rate of C-14 Uptake. Generally, eucaryotic ultraphytoplankton are dominant because of their high cell-specific rate of C-14 uptake and in spite of their relatively low abundance. Less often, it seems, procaryotic picoplankton may dominate in spite of their low cell-specific rate of C-14 uptake because of their high abundance.