Species specific primary production measurements of Arctic phytoplankton

Abstract

In the eastern Canadian Arctic, algae greater than 1·0 μm in diameter dominated both phytoplankton biomass and primary production. In these waters, correlations between cell volume, cellular chlorophyll a (chl a) or chl a: cell volume and cellular primary production (pg C h-1 cell-1) were not significant at the individual species level. Correlations were significant only when all data were pooled or treated as taxonomic groups of diatoms and dinoflagellates. In individual species a weak dependence was observed between the cellular chl a or chl a: phaeophytin and the carbon assimilation ratios (pg C h- pg-1 chl a). Assimilation ratios for individual species fall into a narrow range (0·06–1·31), similar to that observed on bulk natural Arctic phytoplankton or on senescent cultures. On a cell basis, however, the production ratios varied widely (8–9220 pg C h-1 cell-1), with marked intraspecific variations, suggesting that the cells are accumulating chl a in excess of their division. Thus, chl a in the Arctic waters seems to have limited utility as a unit of biomass for normalizing photosynthesis. The observed wide differences in the interspecific and intraspecific photosynthetic rates (pg C h-1 cell-1) are of the same magnitude as those from bulk algal cultures.