Metal uptake in a coastal diatom influenced by major nutrients (N, P, and Si)

The influence of major nutrient additions on trace metal uptake (Cd, Se, and Zn) in a coastal diatom Thalassiosira pseudonana was investigated. A short-term exposure (5 h) was employed to measure the concentration factor (ratio of metal concentration in the cells to metal concentration in the medium) which was used as a kinetic parameter to quantify the relative rate of metal uptake in the cells. Following an initial rapid surface sorption, a linear pattern of uptake over time was typical for Cd, Se and Zn, indicating that these metals may have been transported intracellularly during the short-term exposure period. N addition significantly increased the rates of Cd uptake in the cells. Although the concentration factor of Zn increased with N addition, statistical analysis indicated that N addition did not significantly affect the rate of Zn uptake in the cells. Se uptake in the cells was independent of N additions, but was lowered with increasing Si concentration. Si addition did not significantly affect Cd and Zn uptake. Similarly, P addition did not influence the rates of metal uptake in the cells. There was a significant correlation between the rate of uptake of Cd and Zn and the cell growth rate. This study demonstrated that water quality brought about by a change in nutrient condition could considerably influence the uptake of metals by marine phytoplankton.