Temporal and spatial distribution of diatom assemblages and their relationship with environmental factors in Balikhli River (NW Iran)

Abstract Benthic diatom assemblages on the natural substrata at Balikhli River (northwest Iran) were investigated monthly. A total of 96 samples were collected from epilithic and epipelic substrata. A total of 110 taxa from 49 genera were identified. The most abundant diatom species were Cyclotella meneghiniana , Diatoma moniliformis , Nitzschia inconspicua , Planothidium lanceolatum and Gomphonema olivaceum . Non-metric multidimensional scaling (NMDS) analyses were performed to visualize relationships between diatom communities from different samples, substrates, seasons and sites. Although n-MDS analysis revealed explicit differences between diatom communities of two substrate but common diatom taxa were not restricted to single substrates. The nMDS analysis showed differences between summer and autumn samples. Diatom composition was diverse at every investigated site. SIMPER analysis determined the most representative taxa of the statistically different groups of seasons, stations and substrates. Cluster analysis of samples identified three major groups based on diatom assemblages. Canonical correspondence analysis (CCA) of groups resulted from cluster analysis, showed that the nutrient concentration gradient, pH were the most important factors affecting the composition of diatom assemblages and species distribution. The findings of this study denote that the main determinants of variation in benthic diatom communities of Balikhli River result from a combination of land use patterns caused by human activities, river hydrology and natural phenomena including geology.