The influence of zinc, aluminum and cadmium on the uptake kinetics of iron by algae

The uptake of iron by the marine diatom Thalassiosira weissflogii and the green algae Dunaliella tertiolecta in seawater has been investigated. Computations were made of the rate constants for the binding of iron to specific cell surface-associated transport ligands and the subsequent slow active uptake into the cytoplasm of the cells. Although both algae transport Fe, the sorption constants and the kinetic parameters are markedly different and temperature dependent. The sorption constants, which are one order of magnitude higher for T weissflogii versus D. tertiolecta (2.5 × 10−9 1 cell−1 vs. 2.2 × 10−10 1 cell−1) at 25 °C, give us a measure of the theoretical number of transport sites needed by each cell. The effects on the iron speciation and on the rate of iron uptake due to the addition of different concentrations of Zn(II), Al(III) and Cd(II) have also been determined. The results confirm that while iron is taken up via specific sites on the cell surfaces, synergistic and antagonistic effects on the iron rate uptake for T. weissflogii and D. tertiolecta, respectively, have been found and evaluated.