Cadmium accumulation by several seaweeds

Cadmium (Cd) accumulation by five species of seaweeds was studied with particular attention to Gracilaria tenuistipitata, which grew well in coastal regions with fresh water influx. These species accumulated Cd in the range of 223–496 μg/g dry weight within 6 days of exposure. The LC50 of Cd in culture medium to G. tenuistipitata was determined to be 0.3 g/1. Cadmium uptake by G. tenuistipitata followed a biphasic kinetics. A rapid phase of accumulation occurred within 2 days followed by a slow phase during prolonged treatment. Greater than 50% of the accumulated Cd was bound firmly to the algae 10 days after the algae were placed into Cd-free seawater following previous exposure to Cd. Cadmium accumulation was proportional to the external Cd concentration under sublethal Cd concentrations. G. tenuistipitata accumulated much less Cd in darkness than in the presence of light, implying that the Cd uptake process is at least partially energy dependent.