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.
