Abstract
Toxic blooms consisting of Prymnesium parvum CARTER and Prymnesium patelliferum GREEN, HIBBERD … PIENAAR have caused variable degrees of mortality off armed fish in the Sandsfjord system, southwestern Norway annually between 1989 and 1996. Cultures of {P. parvum} and P. patelliferum were established from water samples during the bloom in the Sandsfjord system in 1993. In order to investigate possible differences in reproduction rates and autecology between the two species, growth as a function of different salinity, photon fluence rates (PFR) and temperatures of the two Norwegian strains was compared with the corresponding growth of strains of P. parvum from England and Denmark, and strains of {P. patelliferum} from Australia and England. The toxicities of the same strains grown under varying salinity, light and temperature conditions, were also compared. Maximum growth rates were generally higher in P. patelliferum than in P. parvum, but strain differences within the species varied significantly. Both optimal growth conditions and toxicity differed greatly between the strains, and seem to be more linked to the individual strains than to species. Furthermore, there was no apparent relationship between toxicity and salinity, temperature or PFR. Thus, there were no marked differences in autecological and toxic properties between P. parvum and P. patelliferum apparent from this investigation.
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