Relationship between macroinvertebrate and environmental variables in Hengshishui River,Guangdong,China

The relationship between macroinvertebrates and environmental factors at 14 sites on the Hengshishui River was studied by Canonical Correspondence Analysis(CCA).The species-environment correlations in the dry season and wet season were both higher than 90%,which indicated the distribution of macroinvertebrates in Hengshishui River was strongly affected by environmental factors measured.Chemical oxygen demand(COD) and pH were the two major factors affecting macroinvertebrate distribution in the dry season.Turbidity and heavy metal concentrations(such as copper and lead) were also influential on macroinvertebrate distribution to some extent.In the wet season,copperand lead concentrations,and pH were the most important factors influencing macroinvertebrate distribution.At the species level,the abundance of pollution tolerant species such as Ceratopogonidae,Chironmidae and Tipulidae were positively correlated with the environmental axes of COD and heavy metal concentration,but the sensitive species such as Gastro