AME 61:141-148 (2010)  -  DOI: https://doi.org/10.3354/ame01444

ABSTRACT: The haptophyte flagellate Prymnesium parvum forms blooms in brackish waters and produces toxins that harm aquatic organisms. Batch cultures of P. parvum were grown in phosphorus-limited artificial seawater medium with 3 treatments: no aeration or buffering, continuous aeration, and buffering to a high, basic pH. Over a period of 32 d, frequent samples were taken to determine: cell abundance; cellular composition of carbon (C), nitrogen (N), and phosphorus (P); culture pH; and hemolytic activity. Only pH differed significantly among media treatments: it was basic in all treatments after 10 d of culture, but consistently highest in the buffered medium treatment. In all treatments, exponential population growth was observed during the first 10 d of culture, at rates of about 0.4 to 0.6 d^–1. The cell quota for P declined rapidly over the first 8 d of culture and more slowly thereafter. A transition from exponential growth to stationary phase occurred over 10 to 21 d of culture. Population growth rate was related to cell quota for P according to Droop’s equation, with an estimated quota for zero growth of about 5 fmol cell^–1. In all cultures, high hemolytic activity was seen on Days 8 and 12. All but one culture displayed oscillations of hemolytic activity thereafter. At times of high hemolytic activity, the cell quota for P was <100 fmol cell^–1 and the cellular C:P ratio was at or above the Redfield ratio of 106.

KEY WORDS: Harmful algae · Phytoplankton · Blooms · Toxins · Cell quota · Nutrient limitation · Phosphorus