Phosphorus Utilization and Storage in Batch Cultures of the Dinoflagellate Peridinium Cinctum F. Westii1

Peridinium cinctum f. westii (Lemm.) Lef., a dominant species in the phytoplankton of Lake Kinneret was studied in batch cultures. External orthophosphate concentrations were depleted by successive transfers to increasingly lower initial orthophosphate concentrations (P0) of 200, 50, 5, 0.6 and 0.2 μM (culture cycles of 45–64 days). Lower cell yields were obtained as P0 decreased, but growth rates were unaffected. The decrease in an intra‐cellular P pool unextractable by cold 6% trichloroacetic acid (TCA) was shown to be responsible for the effect on cell yields. A 31P nuclear magnetic resonance (NMR) study revealed that the major constituents of this internal phosphorus pool in phosphate‐rich cells were the polyphosphates, organized in rigid aggregates of low mobility. Electron‐dense bodies which were observed in phosphate‐enriched P. cinctum cells further supported the existence of an aggregate structure of the polyphosphates. It is concluded that P. cinctum stores excess orthophosphate as polyphosphates which accumulate in a rigid morphological structure.