Acute and chronic effects of toxic metals on viability, encystment and bioluminescence in the dinoflagellate Gonyaulax polyedra

摘要

Toxicity bioassays based on survival were carried out with cells of the marine dinoflagellate Gonyaulax polyedra exposed to mercury (Hg~(2+)), cadmium (Cd~(2+)), lead(Pb~(2+)) and copper (Cu~(2+)). The toxicity scale of these metals found was Hg~(2+) > Cu~(2+) > Cd~(2+) > Pb~(2+). Cells exposed to metals promptly underwent encystment, which is an important strategy for surviving metal exposure. Following 48 h exposure to Cu~(2+), complete excystment occurred within 96 h after reinoculation of cells in fresh metal-free media, and with Pb~(2+) partial recovery occurred in that time. Bioluminescence was affected by the metals in a dose-dependent manner primarily by increasing the frequency of flashing, but the glow emission was also altered with acute Cu~(2+) and Pb~(2+) treatments. Several physiological processes in G. polyedra are under circadian control. Chronic exposure to metals caused no substantial alterations in the circadian rhythm of bioluminescence glow, indicating that the biological clock of this dinoflagellate is not sensitive to these metals at the concentrations tested.