Abstract
We identified 209 species of algae and cyanobacteria at 4 sites in the Kabul River. Green algae, diatoms, and charophytes dominated in the river, which reflects regional features of agricultural activity. Species richness and algal abundance increased down the river. The Water Quality Index characterizes the quality of water down the river as medium to bad. The index of saprobity S reflects Class III water quality. The Water Ecosystem Sustainability Index (WESI) shows contamination with nutrients. According to the River Pollution Index (RPI), waters in the river have low alkalinity and low salinity, and are contaminated with nutrients. Pearson coefficients showed that water temperature plays a major role in the total species richness distribution (0.93*) and in the green algae distribution (0.89*), while cyanobacteria were stimulated also by water salinity (0.91*). Stepwise regression analysis indicated water temperature as the major regional factor that determines riverine algal diversity. Surface plots and Canonical Correspondence Analysis (CCA) showed that salinity, nitrates, temperature, and Biochemical Oxygen Demand (BOD) can be defined as major factors affecting algal diversity. Dendrites mark the upper site of the Warsak Dam as the source of the community species diversity. Bioindication methods can give relevant and stable results of water quality and self-purification assessment that can be employed to monitor the regional water quality.