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

A partitioning of ultraphytoplankton primary production among prochlor ophytes, cyanobacteria, and eucaryotic algae was made by shipboard flo w cytometric sorting of C-14-labeled cells. Aggregate primary producti on was derived from the sum, over all three ultraplankton groups, of t he product of cell abundance and cell-specific rate of C-14 uptake whi ch ranged from 0.03 to 4 fg C cell-1 h-1 for prochlorophytes and 0.2 t o 10 fg C cell-1 h-1 for cyanobacteria. Results indicated that the dom inant primary producer was not necessarily the numerical dominant nor necessarily the group with the highest cell-specific rate of C-14 Upta ke. Generally, eucaryotic ultraphytoplankton are dominant because of t heir high cell-specific rate of C-14 uptake and in spite of their rela tively low abundance. Less often, it seems, procaryotic picoplankton m ay dominate in spite of their low cell-specific rate of C-14 uptake be cause of their high abundance.