富营养化水体中N、P浓度对浮游植物生长繁殖速率和生物量的影响

Effect of N,P concentration on growth rate and biomass of phytoplankton in eutrophical water

在浮游植物生长繁殖的高峰期(7～10月份)对3个富营养化水体的总氮、总磷和浮游植物生物量进行调查,统计分析了生物量与氮和磷浓度的关系。利用3种水样和梯度稀释的东湖水样培养玫瑰拟衣藻(Chloromonasrosae),研究了氮、磷浓度对生长繁殖速率的影响。结果表明磷是生长繁殖速率的限制因子,求出了生长繁殖速率与磷浓度的对数回归方程y=0.0806lnx+0.4658,当磷浓度小于0.05mgL时,生长繁殖速率随着磷浓度的升高而直线上升,当磷浓度进一步升高,生长繁殖速率仍然随之增加,但增加的幅度越来越小,当磷浓度达到0.2mgL时,生长繁殖速率基本不再随着磷浓度的增加而升高。计算出生长速率为零时磷的浓度是0.003mgL,接近贫营养化湖泊磷浓度的下限,计算结果与坂本的调查统计结果相吻合,说明回归方程具有代表性。在调查的3个富营养化水体中,浮游植物中的氮占全部氮元素的53%,磷占全部磷元素的85%,是氮、磷存在的主要形式,所以,评价水体的营养程度,必须同时考虑水中溶解的氮、磷和生物体内的氮、磷。统计分析表明,3个富营养化水体中浮游植物的生物量由氮(溶解氮+胞内氮)和磷(溶解磷+胞内磷)的浓度共同决定,生物量与氮浓度的直线回归方程y=10.687x-7.8304,生物量与磷浓度的直线回归方程y=122.11x-12.069。实验结果为根据氮、磷浓度以Redfield值判断浮游植物限制性营养元素的相对性和绝对性提供了例证。对3个富营养化水体的比较表明,防止水体富营养的唯一办法是维持水体氮、磷等主要营养元素收支平衡,治理富营养化的根本办法是从水体中移走过量的氮、磷等主要营养元素。

Total nitrogen, total phosphorus, biomass in three eutrophic waters were investigated in the rapid-growth season of phytoplankton （July - October）. Chloromonas rosae was cultivated in water samples from three eutrophic waters and diluted water samples from Lake Donghu to determine the effect of N and P concentrations on growth rate. The relationship between biomass and N and P concentrations, analyzed by regression, showed that phosphorus was the limiting factor for algae growth in eutrophic water. The relationship between growth rate and P concentration can be described with the regression equation y = 0. 08061nx ＋ 0.4658, （ R^2 = 0. 889）. Growth rate increased linearly with the increase of P concentration when it was below 0.05 mg/L, Growth rate was less increased when the P concentration was above 0.05 mg/L, and was almost unaffected when the P concentration exceeded 0.2mg/L. The P concentration corresponding to growth rate ＂0＂ （deduced from a regression equation） was 0.003 mg/L, close to the minimal P concentration of poor nutrient lakes. This indicated that the regression equation was representative, The average values for planktie of eutrophy, N and P both cellular N and P in the three eutrophic waters were respectively 53 % and 85 %. To evaluate the levels in the water and in the plants must be considered. The biomass of phytoplankton is controlled by concentrations of both dissolved and cellular N and P. The following linear regression equations describe the relationship between biomass and N： y = 10.687x -7. 8304, （R^2 = 0. 950）, biomass and P, y = 122.11 x - 12. 069, （R^2=0. 991 ） They exemplify the absolute and relative aspects of growth,limiting factors with Redfield values. We conclude that the only way to prevent eutrophication is to maintain a balance between the input and output of nutrients and to remove excessive dissolved N and P in the water.