氮、磷对两种微藻吸附与吸收镍的影响

EFFECTS OF N,P ADDITIONS ON ABSORPTION AND UPTAKE OF NICKEL IN TWO MICROALGAE

采用放射性同位素示踪的方法,研究了大量营养盐氮和磷添加对两种微藻:东海原甲藻(Prorocentrum donghaienseLu)和中肋骨条藻(Skeletonema costatum)吸附和吸收重金属镍的影响。结果表明,在短时间(2h)的培养实验中,大量营养盐的添加影响了藻类对重金属的吸附和吸收速率,但氮、磷浓度的增加对藻类吸附和吸收镍的影响有所差异:硝酸盐浓度的添加促进了藻类对镍的吸附和吸收,磷浓度的添加促进了两种藻类对镍的吸附,但对藻类吸收镍的影响不大。在未添加营养盐的条件下,东海原甲藻对镍的吸附量要高于硝酸盐添加组但吸收量则较低,而中肋骨条藻的吸附量和吸收量均较硝酸盐添加组低。当尿素为氮源时,尿素促进了藻类对镍的吸收,其吸收量为同一浓度硝酸盐的1·2倍。本研究结果证明,近海富营养化特别是氮浓度的增加会影响浮游植物对微量金属的吸收,进而可能会影响到金属在整个海洋食物链中的传递。

This study examined the influences of major nutrients （N, P） additions on absorption and uptake of an essential bioactive trace element, nickel （Ni） in two microalgal species, Prorocentrum donghaiense Lu and Skeletonema costatum using radioisotope method. Relative metal absorption and uptake were quantified by kinetic measurement of metal concentration factor over a short exposure period （2h）. Our study demonstrated that nutrient additions influenced the metal absorption and uptake rate together with cell growth rate in two microalgal species. The increase in ambient N concentrations enhanced metal absorption and uptake rate by the cells. The metal uptake of P. donghaiense and S. costatum increased by 1.5 and 2.5 times, and the metal absorption of P. donghaiense and S. costatum increased by 1.5 and 2 times over the range of 20- 320μmol/L. Statistical analysis proved that N addition influenced significantly the Ni uptake and absorption in both P. donghaiense and S. costatum. The effects of P addition on metal uptake and absorption were less pronounced than those of N addition. The increase in ambient P concentration enhanced metal absorption in two microalgal species while it had no effects on metal uptake. Under most circumstances the metal uptake rate increased exponentially with the increase of growth rate. Metal absorption in P. donghaiense cells without addition of N was higher than that with addition of nitrate, but metal uptake was lower, while both metal absorption and uptake in S. costatum cells without addition of N were lower than that with addition of N. Urea additions enhanced Ni uptake with urea as the nitrogen source compared to those with nitrate as nitrogen source, the uptake increased 1.2 times. Our study demonstrated that nutrient enrichments especially N addition in many coastal waters could considerably affect trace metal uptake and absorption in phytoplankton and presumably metal trophic transfer in marine food chains.