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 carterae and Prorocentrum micans growing exponentially was examined in batch cultures. The concentration of labile copper (free ion plus that present in labile complexes) in the cultures was estimated taking into account the pH of the medium at the moment of copper addition, and the chemical composition 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 of 1·58 μM (100 μg dm -3 ) of total copper, showed a decrease in the growth of the cultures. Related to the number of cells in the cultures, these labile copper concentrations correspond to, respectively, 3·80 and 19·8 fmol of dissolved copper per cell. Growth of the two species in lower copper concentrations was similar to the growth of the control cultures. Besides a decrease in the growth of the cultures, higher copper concentrations also induced changes in cell motility. At the two highest copper concentrations a decrease in the protein content, only studied in P. micans, was observed. In P. micans, lethality was achieved with a concentration of labile copper of about 3·16 μM (406 fmol dissolved copper per cell) [resulting from 15·8 μM (1000 μg dm -3 ) of total copper]; there was both an irreversible loss of cell motility and growth inhibition (over the 21 days considered) and a large reduction in protein. Both species showed a certain ability to recover from sublethal copper doses. Copper effects and the difference in sensitivity of the two dinoflagellates to the metal are discussed.