EFFECT OF NITROGEN OR PHOSPHORUS STARVATION ON PIGMENT COMPOSITION OF CULTURED HETEROCAPSA SP

The effect of nitrogen (N) and phosphorus (P) depletion on the cell volume and pigment composition of the marine dinoflagellate Heterocapsa sp. was studied. Cell size increased under both N or P starvation. but the change was faster when P was limiting. Quantitatively, N deficiency resulted in greater pigment loss than did P deficiency, thereby corroborating the relationship between pigment synthesis and N metabolism. It is suggested that the synthesis of pigments is primarily stopped at a transcriptional level (from DNA to RNA) under P limitation and at a translational level (from RNA to proteins) under N limitation. Almost all pigments underwent a parallel decrease during the stationary phase and no clear changes in pigment ratios were found. As an exception, a pigment identified as diatoxanthin accumulated in the algae when cell growth ceased. This occurred regardless of the growth-limiting nutrient and became more pronounced as cell deterioration progressed.