Among thousands of known species of phytoplankton we find the genre Pseudo-nitzschia. On 37 at present described species (and only 28 tested), 14 are capable of producing an amnesic toxin, the domoic acid, deadly for the human being but also for the birds and the marine mammals. The production of domoic acid depends not only on species, but also on strains and their environment. To understand better when and why this toxin is produced, it thus seems important to be interested in the physiology of the cell. The purpose of this thesis was to test the effect of various biotic and abiotic factors not only on the production of domoic acid but also on the physiology of cells. The effect of competition with bacteria and an other diatom was tested on Pseudo-nitzschia sp., as well as limitations on iron and/or copper or copper toxicity.
