We assess here a method for determining what contribution various components of natural phytoplankton assemblages make to measured community primary productivity. Following incubation with 14C-bicarbonate-labelled plankton and unlabelled controls are physically separated into sets of parallel subpopulations by centrifugation in density gradients. The relative activity of the former subaliquots is determined by scintillation counting while the latter subaliquots are enumerated by a modified Utermohl inverted microscope method. Field and laboratory data are presented illustrating partitionings of coastal and oceanic plankton population carbon uptake. The described procedure could be used to partition the uptake of other isotopes or biomass parameters such as chlorophyll or ATP concentration. The advantages and disadvantages of the density gradient approach are discussed relative to available alternatives.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Aquatic Science