NUTRITIONAL-STATUS AND PIGMENT COMPOSITION OF PHYTOPLANKTON DURING SPRING AND SUMMER PHAEOCYSTIS BLOOMS IN DUTCH COASTAL WATERS (MARSDIEP-AREA)

The general nutritional status and pigment composition of the phytopla nkton population during the 1991 spring and summer Phaeocystis blooms in Dutch coastal waters was analysed using the 480/665 nm absorption r atio of 90% acetone extracts as well as reverse-phase HPLC-pigment ana lysis. A 100% increase in this ratio was indicative of moderate nutrie nt deficiency at the end of the Phaeocystis spring bloom in the Marsdi ep area. During the summer, nitrate was more likely to be the limiting nutrient than phosphate. Both physiological adaptation and species co mposition were found to influence the absorption ratio. Variations in the absorption ratio did not completely reflect the variations in fuco xanthin and chlorophyll a. Therefore it was concluded that besides nut rient limitation dynamics, the variable abundances of in particular ch lorophyll-c3 containing species (such as Prymnesiophyceae) may affect the absorption ratio.