RESTING SPORE FORMATION AND PHOSPHORUS COMPOSITION OF THE MARINE DIATOM CHAETOCEROS-PSEUDOCURVISETUS UNDER VARIOUS NUTRIENT CONDITIONS

The marine diatom Chaetoceros pseudocurvisetus was used for a study of resting spore formation and cellular phosphorus composition. Resting spores were found in any culture medium with ample silica, including n itrogen limited, phosphorus limited and nutrient replete conditions. R esting spores protected themselves with thick silica walls, so that ve getative cells required about 3 pmol cell(-1) of additional silica to form resting spores. Phosphorus compounds in the cells were divided in to eight fractions: nucleotide-P, orthophosphate, acid soluble polypho sphate, sugar phosphate, nucleic acid-P, acid insoluble polyphosphate, lipid-P and residual-P. The sum of orthophosphate, sugar phosphate an d nucleic acid-P comprised over 65% of the total phosphorus in cells u nder any culture conditions. Sugar phosphate was the most variable com ponent, being most abundant in vegetative cells and least abundant in resting spores.