基于Logistic方程描述的鱼食和阿特拉津共同作用对铜绿微囊藻生长的影响

在养殖水域中地表径流等可引起水域中除草剂浓度升高，威胁养殖水环境的生态平衡.为评价阿特拉津和鱼食在水环境中的生态风险，以ρ（阿特拉津）（0、5、10、20和40 μg/L）及鱼食（鱼食为MⅡ培养基中的氮、磷营养源）投加量（0.05、0.20 g；d < 0.85 mm）为变量，基于Logistic方程探讨阿特拉津和鱼食共同作用下铜绿微囊藻（Microcystis aeruginosa）的生长，并研究藻类生长对鱼食营养盐的利用.结果表明:在ρ（阿特拉津）为0~40 μg/L范围内，铜绿微囊藻生长曲线均可用Logistic方程描述（R2=0.975~0.996）；一般情况下，基于Logistic方程得到的比生长速率、增殖速率和抑制率拟合公式均可描述相应实测值的变化，相关性分析得到的拟合值与实测值相关系数（R2）分别为0.861~0.992、0.381~0.839和0.621~0.839.相同ρ（阿特拉津）下，鱼食投加量对藻细胞密度有显著影响（P < 0.05），Logistic方程拟合得到的理论最大藻细胞密度（K）随鱼食投加量的增加而增大.相同鱼食投加量下，ρ（阿特拉津）为5~40 μg/L时对藻类生长有抑制作用，随ρ（阿特拉津）增加，抑制强度逐渐升高，藻细胞密度越低，最大藻细胞密度随ρ（阿特拉津）的增加而减小.藻细胞密度与PO₄3--P利用量之间关系可用方程N=a×△cb描述，R2为0.23~0.99；藻细胞密度与NH₄+-N利用量之间关系可用方程N=a+b×△c描述，R2为0.04~0.99；藻细胞密度与TN/TP、NH₄+-N/TN和PO₄3--P/TP的关系均可用幂函数方程N=a"xb'描述，R2分别为0.72~0.78、0.66~0.83和0.55~0.56.研究显示，Logistic方程可用于分析阿特拉津和鱼食对铜绿微囊藻生长的影响，且藻类生长与营养盐质量浓度之间存在一定的定量关系. 

Characterizing Combined Effects of Fish Food and Atrazine on Microcystis aeruginosa Growth by the Logistic Function

Herbicide runoff can contaminate aquaculture and disturb ecological balance. In order to evaluate the ecological risks of atrazine and fish food on the aquatic environment, we studied the effects of atrazine on Microcystis aeruginosa growth using the Logistic function and the relationship between algae density and the concentration of nutrients in the fish food culture medium. Different concentrations of atrazine (0, 5, 10, 20 and 40 μg/L) and fish food dosages (0.05 and 0.20 g; d < 0.85 mm) were added to MⅡ culture mediums; fish food was used as the source of nitrogen and phosphorus. The results showed that M. aeruginosa growth can be fitted well by the Logistic function with 0-40 μg/L atrazine (R2=0.975-0.996). Fitted functions of specific growth rates and inhibition rates based on the Logistic equation can be used to describe their experimental values generally. The correlation coefficients (R2) were 0.861-0.992, 0.381-0.839 and 0.621-0.839, respectively, by correlation analysis between corresponding fitted and measured values. With the same concentration of atrazine, the dosage of fish food had a significant effect on algae cell density (P < 0.05). The maximum algae cell density (K) of M. aeruginosa calculated by the Logistic function increased with increasing dosages of fish food. With the same dosage of fish food, atrazine (5-40 μg/L) inhibited the growth of M. aeruginosa, and the inhibition rate increased with increasing atrazine concentrations, while K decreased with increasing atrazine concentrations. The relationship between algae cell densities and nutrient usage can be fitted by different functions:dissolved orthophosphate (PO₄3--P) by function N=a×△cb (R2=0.23-0.99); ammonia nitrogen (NH₄+-N) by function N=a+b×△c (R2=0.04-0.99). We further explore relationships between algae densities and nutrients ratios:TN/TP ratio, NH₄+-N/TN ratio and PO₄3--P/TP ratio by fuction N=a"xb'(R2=0.72-0.78, 0.66-0.83 and 0.55-0.56, respectively). In summary, the Logistic equation can be used to characterize the effect of atrazine and fish food on the growth of M. aeruginosa, and there is a certain quantitative relationship between M. aeruginosa growth and nutrients.