老虎潭水库浮游植物群落特征及水生态健康评价

Phytoplankton community composition and health status assessment of aquatic ecosystem in Laohutan Reservoir

2020年2、5、8月对浙江省湖州市老虎潭水库水质理化指标及水生态指标进行调查,分析了该水库浮游植物群落结构特征及优势属,并应用典范对应法分析了浮游植物与环境因子之间的相关性,运用水质生物学评价法、综合营养状态指数法(TLI)进行水质评价。同时,为更好了解老虎潭水库水生态系统健康状况,选取了水体理化指标(SD、DO、COD_(Mn)、TN、NH_(3)^(-)N、TP和SS)和水生态指标(浮游植物生物量、浮游动物生物量、Chl a、底栖动物生物量、浮游植物多样性指数)12个指标,构建了老虎潭水库水生态系统健康评价指标体系,并基于客观熵权法的生态系统健康综合指数法(EHCI)对老虎潭水库进行水生态系统健康评价。结果表明:老虎潭水库浮游植物共7门44属,绿藻门、硅藻门和蓝藻门是老虎潭水库浮游植物组成的主要门类。浮游植物丰度为(4.4~102)×10^(6) cells/L,生物量为0.79~37.23 mg/L;其主要优势种属呈现出冬季蓝藻-硅藻门型,春季则主要为硅藻门,夏季优势种属多集中在绿藻门。通过典范对应分析发现,Chl a、COD_(Mn)、DO、SD、TN是影响老虎潭水库浮游植物群落变化的最重要环境因子。Shannon-Wiener多样性指数月均值为2.57,整体呈现出β-中污型水质;而Pielou均匀度指数月均值为0.63,整体均呈现出清洁-寡污型水质。老虎潭水库TLI指数和EHCI指数月均值分别为44.0和0.4003,前者评价水体为中营养水平,后者评价得出水库整体处于中等健康状态。同时,TLI指数和EHCI指数呈显著的负相关关系,说明两者的评价结果相对吻合,但EHCI指数更能体现出老虎潭水库生态系统健康评价的整体性和综合性,评价结果更明确,对老虎潭水库的后续有效管理具有更为重要的现实意义。

The water quality physicochemical factors and the aquatic organism parameters of the Laohutan Reservoir,an important centralized drinking water source in Huzhou,in the Zhejiang Province of China,were surveyed at five sampling sites on February 26,May 6 and August 26,2020.The seasonal variations of phytoplankton community and dominant genus were investigated and simultaneously,a canonical correspondence analysis(CCA)was used to analyze the correlations between the phytoplankton community structure and environmental factors.Meanwhile,the bioassessment of phytoplankton and the comprehensive trophic level index(TLI)were used in the water quality assessment of Laohutan Reservoir.To explore the aquatic ecosystem health of Laohutan Reservoir,an indicator system for aquatic ecosystem health assessment was established by selecting 7 water quality parameters(i.e.,SD,DO,COD_(Mn),TN,NH_(3)^(-)N,TP and SS)and 5 aquatic organism parameters(i.e.,phytoplankton biomass,Zooplankton biomass,Chl a,Benthic biomass and Phytoplankton diversity index)of Laohutan Reservoir to build the aquatic ecosystem health assessment indicator system.Moreover,the ecosystem health comprehensive index(EHCI)based entropy weight was used to assess the degree of aquatic ecosystem health of Laohutan Reservoir.The results showed that a total of 44 genera,7 phyla of phytoplankton was identified.Among these species,Chlorophyta,Diatomophyta,Cyanophyta were the most abundant.The density and biomass of phytoplankton were(4.4~102)×10^(6) cells/L and 0.79~37.23 mg/L,respectively.Seasonal succession of the dominate genera of phytoplankton was significant different.In winter,the dominate genera present to be the Diatom-Blue algae type,and the most genera was Melosira and Pseudoanabaena;and in spring it present to be the Diatom type,the most species was Achnanthes and Synedra,then in summer,the dominate genera present to be the Green algae type.Chl a,COD_(Mn),DO,SD and TN were the main factors affecting the quantity and distribution of phytoplankton populations.The monthly average Shannon-Wiener diversity index(H′)of Laohutan Reservoir was 2.57,and the pollution level wasβ-mesosaprobity;While the monthly average Pielou evenness index(J)was 0.63,and the pollution level was clean-oligosaccharide type.The data of H′and J were the highest in summer and the lowest in spring.The monthly average TLI and EHCI were 44.0 and 0.4003,respectively,while TLI indicated that the water quality of Laohutan Reservoir was mesotrophic level and EHCI showed that the healthy level of Laohutan Reservoir ecosystem is middle.In addition,the correlation analysis between TLI and EHCI showed significant negative correlation(P<0.05),indicated that the results of assessment evaluation was relatively consistent.Otherwise,the ecosystem health assessment by EHCI method based entropy weight could better reflect the integrity and comprehensiveness of ecosystem health assessment in Laohutan Reservoir.Finally,the water ecological health assessment system and the water ecological health assessment results in this study are of great practical significance for the management of Laohutan Reservoir in the future.