Effect of human disturbance on benthic macroinvertabrate assemblages and physicochemical water quality parameters of temsa river, agaro town, south west Ethiopia

Abstract

Background: Rivers are the most productive ecosystems in the world and have values for the fulfillment of human needs and ecological functions. However, different human activities taking place near to the river is posing risk (deterioration) to the ecological and physicochemical quality of the river. Though, increasing impact of human disturbances on the freshwater bodies of Ethiopian rivers calls for efficient and continuous monitoring based on physicochemical river quality parameters and ecological health assessment. Objective: To assess the effect of human disturbances on benthic macroinvertebrate assemblages and water quality of Temsa river, Agaro town, south west Ethiopia. Methods: A cross-sectional study was carried out on April, 2019 in the dry season. Macroinvertebrates and water samples were collected from thirteen sampling sites along the river. The samples were collected in a polyethylene bottles and transported to the laboratory by using ice box. Samples were analyzed for different physicochemical parameters and various biological metrics. Multivariate data analysis was used to examine the overall relationship among physicochemical parameters and macroinvertebrate assemblages with Principal component analysis, using software program Paleontological Statistics software package for education and data analysis (Past 3.18) version 1.0.0. Findings: A total of 603 macro-invertebrates belonging to 41 families and 12 orders were recorded. From biological metrics Biological Monitoring Working Party score, Shannon diversity index, Ephemeroptera, Odonata and Trichoptera family richness and total family richness portrayed a clear pattern of decreasing with increasing in human disturbance; whereas, family biotic index score, which is an indicator of organic pollution, increased with increasing in human disturbance. Among the physicochemical variables, dissolved oxygen, electrical conductivity, chemical oxygen demand, phosphate and nitrate show significant variation between sampling sites (p < 0.05). Macroinvertebrate metrics, biotic indices biological monitoring working parties and family biotic index showed significant variation at all sampling sites. Conclusions: In conclusion, human activities in and around the river such as farming, solid waste dumping and effluent discharges contribute to the degradation of water quality and decreasing in the macroinvertebrate richness and diversity along the course of the river. Physicochemical parameters (nitrate, phosphate, ammonia) and human disturbances predominantly affecting the macroinvertebrate assemblages in the river study.