The phytoplankton community of Lake Nansihu was investigated seasonally from 2011 to 2014.The effects of phytoplankton diversity (species richness and evenness) on both community biomass and temporal stability were analyzed.A total of 138 phytoplankton species belonging to 78 genera and 8 phyla were identified in the lake.Phytoplankton abundance ranged between 5.09× 105/L and 6.95× 106/L and its biomass varied from 0.44mg/L to 5.46mg/L in different seasons.In spring and winter when the temperature was low,phytoplankton biomass increased with increasing species richness,phytoplankton community with larger number of species was more productive.In summer when the temperature was high,there was a strong negative relationship between phytoplankton biomass and species richness,phytoplankton community with higher diversity had relatively lower biomass.The stability indices of Cyanophyta,Bacillariophyta and total phytoplankton were all unimodally related to phytoplankton species richness.However,the effects of phytoplankton evenness on the Cyanophyta,Chlorophyta,Bacillariophyta or total phytoplankton stability index were not significant (P＞0.05).Results in this research indicated that the effects of phytoplankton diversity on community biomass and temporal stability were complex:species richness had a linear relationship with community biomass and influenced by seasonal variations,a unimodal relationship with temporal stability;evenness had no relationship with either community biomass or temporal stability.%基于2011到2014年对南四湖浮游植物进行的连续监测,研究浮游植物多样性(物种组成和均匀度)与生物量和群落稳定性的关系.结果表明,调查期间共鉴别出浮游植物8门78属138种.湖泊浮游植物细胞密度在5.09×105个/L到6.95×106个/L之间变化,生物量在0.44mg/L到5.46mg/L之间变化.在温度较低的春季和冬季,浮游植物生物量随着物种数的增加而增加,多样性高的群落有更高的生产力.在夏季,浮游植物生物量随着物种数的增加而降低,多样性高的群落具有相对较低的生物量.蓝藻、硅藻和总浮游植物稳定性指数与浮游植物物种数均呈单峰关系.浮游植物均匀度与各个群落稳定性指数的相关系数均不显著.这些结果表明,浮游植物多样性与群落生物量和稳定性有比较复杂的关系:物种数与生物量呈线性关系且受季节变化的影响,与稳定性呈单峰曲线关系;均匀度指数与生物量和稳定性都没有显著的关系.
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