富营养化对两种海洋微藻吸收铜和镉的影响

Influence of eutrophication on metal uptake in two marine phytoplankton species

采用室内模拟实验的方法,研究了不同氮、磷浓度下中肋骨条藻(Skeletonema costatum)和塔玛亚历山大藻(Alexandrium tamarense)吸收重金属Cu和Cd的变化情况。结果表明,10 h的吸收实验中,两种藻对Cu和Cd的吸收量随培养时间呈增长趋势。塔玛亚历山大藻和中肋骨条藻对Cd的吸收速率都与藻生长速率表现出很好的相关性。N浓度的增加显著促进了两种藻对Cu和Cd的吸收。P浓度的增加促进了中肋骨条藻对Cu的吸收,中肋骨条藻对Cd的吸收受P影响不大。P对塔玛亚历山大藻吸收Cu和Cd的影响也不显著。此外,本研究还表明,当外界Cu浓度≤100μg/L,Cd浓度≤20μg/L时,两种藻对Cu和Cd的吸收量随介质中Cu和Cd浓度的升高呈直线增加趋势,说明本实验设置的低、高浓度重金属处理中,藻类的生理状态并未发生明显改变,实验结果准确可靠。

The influences of major nutrients additions on trace metal （Cu and Cd）uptakein two species of marine phy- toplankton （Alexandrium tamarense and Skeletonem acostatum） was examined. During the 10-hour exposure, the meas- ured metal concentration in the two microalgae increased gradually over time. There was a significant correlation be- tween Cd uptake rate and the cell growth rate for both phytoplankton species. Nutrients addition significantly influ- enced the metal uptake rate in all two microalgae species. An increase in ambient N concentration considerably en- hanced 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 μg/L and Cd lower than 20 μg/L.