Studies on the marine planktonic diatom Pseudo-nitzschia. 2. Autecology of P. pseudodelicatissima based on isolates from Danish coastal waters

The effects of variations in salinity (5, 10, 15, 25, 35‰) and temperature (2, 5, 10, 15, 18, 22, 25°C) on growth, valve morphology, and toxicity were examined in the marine planktonic diatom Pseudo-nitzschia pseudodelicatissima (Hasle) Hasle from Danish waters. Growth rates were salinity and temperature dependent. The salinity optimum for growth at all temperatures was 25‰, and no growth was observed at 5 and 10‰. Growth rates increased up to 25°C (higher temperatures were not tested). With one exception (5°C and 25‰), no growth was observed at 2 and 5°C. The lower temperature limit for growth depended on salinity. Morphological variations were not observed among cultures grown under different salinity and temperature regimes. Domoic acid was detected on a few occasions, but no relation between external parameters and toxin production was apparent.