Influence of eutrophication on metal uptake in two marine phytoplankton species

The influences of major nutrients additions on trace metal (Cu and Cd) uptakein two species of marine phytoplankton(Alexandrium tamarense and Skeletonem acostatum) was examined.During the 10-hour exposure, the measured metal concentration in the two microalgae increased gradually over time.There was a significant correlation between Cd uptake rate and the cell growth rate for both phytoplankton species.Nutrients addition significantly influenced the metal uptake rate in all two microalgae species.An increase in ambient N concentration considerably enhanced metal uptake by the cells.The effect of phosphate addition on metal uptake was less pronounced than those of nitrate addition.Only Cu uptake in Skeletonema costatum was enhanced with the increase of ambient P concentration.In contrast to Cd accumulation in Skeletonema costatum and Cu, Cd accumulation in Alexandrium tamarense was not related to the ambient P concentrations.Our study demonstrated that the major nutrient addition, especially N addition in the water can considerably affect the trace metal uptake in phytoplankton and presumably metal trophic transfer in marine food chain.Our experiments also showed that the metal concentration in the cells increased proportionally with elevated ambient metal concentration when the concentration of Cu was lower than 100 g/L and Cd lower than 20 g/L.