氮、磷对镍在食物链上传递的影响

Influence of N, P additions on the transfer of nickel along the food-chain

采用放射性同位素示踪法,研究氮或磷添加对镍在东海原甲藻(Prorocentrum donghaienseLu)和中肋骨条藻(Skeletonema costatum)胞内累积的影响;并将其分别投喂中华哲水蚤(Calanus sinicus)后,探讨镍在桡足类体内的吸收和生理周转。结果表明,经过24h暴露后,氮或磷显著影响这两种藻类对镍的吸收,且高浓度氮或磷均能促进镍在这两种藻类细胞内的累积,因而促进镍在中华哲水蚤体内的吸收;而镍在中华哲水蚤体内的生理周转率却不受氮或磷浓度的影响,似乎更受动物个体的生理状态影响;中华哲水蚤对镍的吸收率与藻类细胞内镍含量呈极显著相关(p<0.001),证明了"桡足类只吸收饵料细胞内的水相金属库"的假说。由此可见,近海富营养化可促进浮游植物对镍的吸收,进而影响该金属在浮游生物食物链上的传递。

We examined the influence of macronutrient （ nitrate or phosphate） additions on the bioaccumulation of Ni in two species of phytoplankton （Prorocentrum donghaiense Lu and Skeletonema costatum）, and its subsequent assimilation and physiological turnover in marine copepod （Calanus sinicus） after ingestion, using a radioactive-tracer method. The results showed that N or P addition significantly influenced intracellular Ni accumulation in the algal cells after 24 h of exposure, with higher ambient N or P enhancing the biological uptake of Ni in the algal ceils. Ni assimilation efficiency by the generally increased with an increase of nutrient concentration in two algal species, due to higher N or P concentration facilitating the uptake of Ni by algae. However, ambient nutritional conditions had insignificant effect on the physiological turnover rate of Ni by the copepod, which seemed to be affected by the physiological conditions of animal individuals. An extremely significant positive-correlation was found between Ni assimilation efficiency by the % intracellular Ni in algal diets （p 〈 0.001）, testifying the hypothesis ＂copepod only assimilates metal in the cytoplasmic pool＂. Therefore, eutrophication may affect the transfer of Ni along the food-chain by facilitating the biological uptake of it by phytoplankton.