ALBERT

Description: This study investigated effects of small-scale turbulence on growth and other selected characteristics of autotrophic planktonic flagellates. Under turbulent conditions generated in the laboratory, experiments in pure batch culture were conducted with Prymnesium parvum (Prymnesiophyceae), Pyrenomonas helgolandii (Cryptophyceae), Prorocentrum redfieldii, Alexandrium minutum, A. fundyense and A. tamarense (Dinoflagellata). Net growth rate of two species were affected by small-scale turbulence, i. e. enhancement in P. parvum, impairment in A. tamarense. In P. redfieldii aggregation and mortality of the cells was enhanced. Except for a slight effect towards smaller cell size in A. tamarense turbulence showed no effect on the size in the six species examined. Carbon and nitrogen content of the cells and their relation were not affected by small-scale turbulence in P. helgolandii and P. redfieldii. The content of chlorophyll a and some accessory pigments was also not affected in the four dinoflagellate species examined. In the three Alexandrium species the cellular contents of mean toxins causing paralytic shellfish poisoning (PSP) were not influenced during the exponential growth stage, but during stagnation and decline, gonyautoxin in A. fundyense increased with increasing turbulence. The effects of small-scale turbulence might also depend on the growth stage of the organisms. Experiments in chemostat cultures instead of batch cultures might be more suitable for investigating the effect of small-scale turbulence in discrete growth stages and are recommended for future experiments.