SOME EFFECTS OF COPPER ON THE DINOFLAGELLATES AMPHIDINIUM-CARTERAE AND PROROCENTRUM MICANS IN BATCH CULTURE

The influence of copper(II) on some aspects of the cell physiology and biochemistry of the dinoflagellates Amphidinium carferae and Prorocen trum micans growing exponentially was examined in batch cultures. The concentration of labile copper (free ion plus that present in labile c omplexes) in the cultures was estimated taking into account the pH of the medium at the moment of copper addition, and the chemical composit ion of the medium. The speciation of other metals was also considered. A. carterae and P. micans exposed to concentrations of labile copper of, respectively, 605 nM and 55 nM, which resulted from the addition o f 1.58 mu M (100 mu g dm(-3)) of total copper, showed a decrease in th e growth of the cultures. Related to the number of cells in the cultur es, these labile copper concentrations correspond to, respectively, 3. 80 and 19.8 fmol of dissolved copper per cell. Growth of the two speci es in lower copper concentrations was similar to the growth of the con trol cultures. Besides a decrease in the growth of the cultures, highe r copper concentrations also induced changes in cell motility. At the two highest copper concentrations a decrease in the protein content, o nly studied in P. micans, was observed. In P. micans, lethality was ac hieved with a concentration of labile copper of about 3.16 mu M (406 f mol dissolved copper per cell) [resulting from 15.8 mu M (1000 mu g dm (-3)) of total copper]; there was both an irreversible loss of cell mo tility and growth inhibition (over the 21 days considered) and a large reduction in protein. Both species showed a certain ability to recove r from sublethal copper doses. Copper effects and the difference in se nsitivity of the two dinoflagellates to the metal are discussed.