氮磷营养盐与有机汞联合作用对微氏海链藻生长的影响

Combined effect of nitrate and phosphate with organic mercury on the growth of Thalassiosira weissflogii

探讨在高营养盐(氮、磷、硅分别为浮游植物生长的营养盐阈值≥40、50、9倍)条件下,氮浓度及氮磷摩尔比值[n(N)/n(P)]变化、汞(甲基汞和乙基汞)对微氏海链藻(Thalassiosi-ra weissflogii)生长的影响。结果表明,高营养盐区海链藻的生长遵循营养盐限制的唯一因子论;氮浓度和氮磷比提高促进生长,当n(N)/n(P)=64则呈抑制效应;生长初期,甲基汞和乙基汞均产生毒性抑制作用,生长中后期,适量甲基汞(浓度≤1.0μg/L)、乙基汞(浓度≤0.5μg/L)却呈兴奋效应,促进生长;汞形态不同,剂量-效应关系不同。氮和有机汞是海链藻生长的刺激因子。适度有机汞污染与氮富营养化对微氏海链藻的生长产生协同效应。

Thalassiosira weissflogii silicate. The concentrations exceeded the was cultured in seawater with high threshold growth limit of marine levels of nitrate, phosphate, and phytoplankton in 40, 50, and 9 times respectively. The influences of different concentrations of nitrate, the ratio of nitrate to phosphate （N/P）, and organic mercury on the growth of T. weissflogii were investigated. The growth was not limited by N/P in the contaminated seawater. The cell densities of T. weissflogii were determined microscopically with a marine phytoplankton arithmometer. The cell densities increased as the concentration of nitrate and N/P increase. But the cell density reached the lowest at N/P of 64. At beginning, the growth of T. weissflogii was restrained by organic mercury, such as methylmercury and ethylicmercury. Later in middle and late stages, methylmercury and ethylicmercury could stimulate the growth at less than 1.0 and 0.5μtg/L, respectively. Combined effect between the nutrient and organic mercury was observed on the growth. Both nitrate and organic mercury were stimulating factors for the growth of T.weissflogii. However, their influences on the growth of T. weissflogii were different depending on mercury species.