Influence of a dam and tributaries on macrobenthos communities and ecological water quality in the Kebir–Rhumel wadi (Northeast Algeria)

The water-quality biomonitoring programs based on macroinvertebrates of the Kebir–Rhumel wadi remain limited. We assessed macroinvertebrate assemblage structure and biological water quality to explore the impact of two discontinuities (a dam and a tributary) on biotic conditions. We sampled site communities above and below the Beni Haroun dam and in two tributaries in April, July, and November 2017. Sites above the dam had lower macroinvertebrate richness compared to reaches below the dam, while the tributaries had a relatively negligible effect on the confluence and mainstem communities. Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa richness; Hilsenhoff Biotic Index (BI); Iberian Biological Monitoring Working Party (BMWP’) index; and Average Score Per Taxon (ASPT) demonstrate a fairly poor quality above the dam and a fair quality below it. One-way analysis of similarity (ANOSIM) and similarity percentage procedure (SIMPER) analyses revealed dissimilar community structures, with pollution-tolerant and pollution-sensitive species most contributing to the dissimilarity between studied reaches. This study has suggested only small changes in macroinvertebrate structure downstream of the dam and no significant impact of tributaries on the mainstem community composition.