Assessing anthropogenic impacts using benthic macroinvertebrate as bio-indicators in central highland streams of Ethiopia

Biological indicators particularly those using macroinvertebrate communities are increasingly used to assess the effects of human driven stressors on stream water and habitat quality.  The goal of this study was to establish relationships between benthic macroinvertebrate and common stressor types (siltation, agriculture and paper mill waste) in central highlands of Ethiopia. For analysis environmental variables and benthic invertebrate taxa were collected from four streams from November, 2011 to June, 2012. There was a significant difference in conductivity, dissolved oxygen, total phosphorus and five days biological oxygen demand between paper mill waste and other stressor types. In siltation sites, most environmental parameters were not significantly different (p > 0.05) from reference and agricultural sites.  Sensitive taxa such as Perlidae, Lepidostomatidae, Scirtidae and Philopotamidae were represented in the reference site. Paper mill waste was the worst stressor for deterioration of water quality and cause significant reduction of benthic invertebrate diversity directly by intoxication and indirectly by changing water quality parameters. Agriculture and siltation stressed sites showed major difference in abundance than richness of benthic invertebrates. Of 39 benthic macroinvertebrate metrics tested, five metrics representing richness, composition and sensitivity were identified as useful to discriminate stressor groups. These metrics are taxa richness, EPT (Ephemeroptera, Plecoptera and Tricoptera), % Oligochaeta & Chironomidae, % EPT-BCH (EPT without Baetidae, Caenidae and Hydropschidae and ASPT (Average Score Per Taxa). Among others % EPT-BCH was found effective to separate the effect of siltation from agriculture and reference sites. This study showed that benthic macroinvertebrate metrics were useful to assess the impact of different stressors in Ethiopian central highland stream and rivers. Key Words: Benthic macroinvertebrate, Stressors, Pollution, Metrics, Highland stream

The water quality degradation of upper Awash River, Ethiopia

Benthic macroinvertebrate based assessment of water quality in the upper Awash River, along the river course of about 500 kms was conducted on quarterly bases between September 2009 and August 2010. This paper reports the complete identification of macroinvertebrates together with measurements of physico-chemical parameters and heavy metal concentrations which were considered as a tool for assessing the water quality status of upper Awash river, Ethiopia. Benthic animals and water samples were collected from three different sampling sites located in the upper Awash River, and analyzed to evaluate stressor sources and the general stream water quality. The percentage abundance of families of various macroinvertebrates taxonomic groups was identified from all sites. Accordingly, Koka bridge site of the upper Awash River had low water quality status which is likely to be due to poor farming, untreated effluents from factories and poor provision of sanitation facilities to the riparian communities. Apparently, the concentrations of the selected nutrients and heavy metals did not differ significantly among the sampling sites (ANOVA, P > 0.05), presumably due to pollution of the whole stream reach by the catchment nutrient sources. Ten orders of benthic macroinvertebrates consisting of 36 families were identified. The highest family richness was observed in Ginchi, slightly impacted site (1) whilst the least faunal diversity was observed in Koka Bridge (7 families) indicating the effect of water quality class differences among the sampling sites.Key words: Macroinvertebrates, organic pollution, heavy metals, water quality, anthropogenic impact, upper Awash Rive