Temporal and spatial variation in population structure of Ephemeroptera in relation to physicochemical properties of Tajan River- Mazandaran province)

Rivers are vital ecosystems and their protection is of outmost importance. In this study effects of physicochemical parameters of water on the population structure of Ephemeroptera in three sampling locations e.g. upstream, middle and downstream of the Tajan River were examined. Sampling was carried out on monthly bases from April to March 2019. One-way analysis of variance was used to evaluate the qualitative status of the sampling stations, Principal component analysis was utilized to determine the effect of environmental factors on separation or overlap of the studied stations and comparative conventional analysis was used to determine the relationship between environmental variables with presence and absence of Ephemeroptera families. Results showed that physicochemical factors varied significantly during the study period. The average of factors such as the flow rate (68.3 m3/sec), dissolved oxygen (9.53 mg/lit) and pH (8.31) were at highest levels in February and March while average of EC (1181µm/cm) and TDS (815 mg/lit) were at their lowest values in in September. Significant differences were observed in physicochemical factors at different stations. The differences were apparent between Mohammadabad station with other two sampling stations in terms of temperature and dissolved oxygen and Tajan station varied significantly with others in terms of EC, TDS and Debi. Significant relationship was observed between frequency and presence of some families of Ephemeroptera including Baetidae with EC and TDS and Oligoneuridae with pH and dissolved oxygen which allows considering these groups as qualitative indicator or indicator species of surface water resources.