Growth and toxicity in Prymnesium patelliferum (Prymnesiophyceae) isolated from Norwegian waters

Abstract

Blooms of Prymnesium causing mortality in farmed fish have been registered in fjords belonging to the Sandsfjord system, southwestern Norway, annually since 1989. These blooms consist of two closely related species, P. patelliferum and P. parvum. Cultures of the former species were established from field samples, and their identity was confirmed by transmission electron microscopy. Growth rates of this P. patelliferum strain were compared with those of an Australian strain of the same species and with a Danish strain of P. parvum. In a 3-month growth experiment at 20 °C, both P. patelliferum strains grew significantly faster than P. parvum. The Australian P. patelliferum strain grew faster than the Norwegian strain at 20 °C, and this difference was accentuated at 28 °C. The optimum salinity range for growth was 8–25‰ for all three strains. All showed toxicity to Anemia nauplii, though the Norwegian P. patelliferum appeared significantly less toxic than the others. In all strains, increased toxicity was seen in phosphorus-deficient cells. Key words: Prymnesium, scale fine structure, growth rate, salinity, toxicity, phosphorus.