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 mu g/g dry weight within 6 days of exposure.
The LC(50) of Cd in culture medium to G. tenuistipitata was determined
to be 0.3 g/l. Cadmium uptake by G. tenuistipitata followed a biphasi
c kinetics. A rapid phase of accumulation occurred within 2 days follo
wed by a slow phase during prolonged treatment. Greater than 50% of th
e 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.