水体富营养化改善过程中浮游植物群落对非生物环境因子的响应:以武汉东湖为例

Responses of phytoplankton community to abiotic environmental variables with the mitigation of eutrophication: A case study of Donghu Lake,Wuhan City

针对武汉东湖存在营养状态梯度的5个子湖(郭郑湖、汤菱湖、团湖、庙湖、水果湖),结合"空间换时间"理论,研究湖泊富营养状况改善过程中浮游植物群落对环境因子的响应.全年调查期间,各子湖综合营养状态指数分布范围为45.4~76.8,浮游植物密度及生物量变化范围分别为2.03×10^6~245×10^6cells/L和0.819~19.9mg/L.冗余分析结果显示,浮游植物的物种分布与水温、总氮、透明度、总溶解性固体、氨氮呈显著相关.采用多元逐步回归分析构建浮游植物密度、生物量与环境因子之间的最优响应方程,结果显示,总氮、水温是影响浮游植物密度的主要因子;对于浮游植物生物量而言,总磷、总氮浓度降低能够降低浮游植物生物量.通过对富营养程度改善进程中浮游植物群落组成的动态变化进行分析,发现浮游植物密度及生物量显著下降,但物种组成及生物多样性并未发生明显转变.此外,浮游植物物种多样性与水体富营养水平梯度并不呈现简单的线性相关.因此,在对富营养化湖泊进行修复时,应制定短期修复与长期维护双重措施,同时应重视生物多样性的重建,进而达到理想的修复效果.

Based on field data and using space-for-time substitution,we discussed how phytoplankton community in lakes responds to mitigating eutrophication.Our field survey and sampling was conducted in five sub-lakes of East Lake in Wuhan: Lake Guozheng,Lake Tangling,Lake Tuanhu,Lake Miaohu,and Lake Shuiguo.The comprehensive trophic state indexes indicated the five sub-lakes were in distinct trophic states,within the range between 45.4 and 76.8.Moreover,the phytoplankton density and biomass were in the range of 2.03×10^6 to 245×10^6 cells/L and 0.819 to 19.9 mg/L,respectively.Results from representational difference analysis showed that the succession of phytoplankton species were significantly related to water temperature (WT),total nitrogen (TN),transparency,total dissolved solids and ammonia nitrogen.We further analyzed the casual relationships between abiotic environmental variables and phytoplankton density/biomass using stepwise multiple liner regression.It was found that TN and WT were the main factors affecting phytoplankton density.Meanwhile,phytoplankton biomass could decrease with the reduction of TN and total phosphorus.Although the total density and biomass of phytoplankton showed a decline with eutrophication mitigation,there was no obvious response in their species composition and biodiversity.Additionally,we found phytoplankton biodiversity and trophic levels showed nonlinear relationship.Therefore,to restore the degraded lakes,short-term and long-term interventions are both needed.Additionally,we should pay more attention to recover biodiversity and ecosystem functions.