Effects of untreated industrial effluents on water quality and benthic macroinvertebrate assemblages of Lake Hawassa and its tributaries, Southern Ethiopia

Abstract

The present study investigates the impacts of industrial effluents on the macroinvertebrate assemblages and water quality of the Lake Hawassa watershed. The water quality and macroinvertebrate assemblages were assessed at 40 sampling sites. The chemical and ecological water quality was evaluated using the Basic Prati index and the Ethiopian Biological Score Index (ETHbios), respectively. Canonical Correspondence Analysis (CCA) was used to evaluate the relationship between abiotic factors and macroinvertebrate metrics. A total of 5 876 invertebrates belonging to twentyfive
families were recorded. The Coleoptera was the most dominant order represented by four families with a relative abundance of 68%. According to the ETHbios scoring system the sites receiving industrial effluent had very poor water quality (ETHbios score <12), whereas the upstream sites had moderate to good water quality (ETHbios 53 to 76). Likewise, the Basic Prati Index of the sites receiving industrial effluent was considered as very heavily polluted (Index score >8). Overall, the industrial effluents had a significant negative impact on water quality and macroinvertebrate diversity. Therefore, proper management of industrial effluent is urgently needed to prevent further deterioration of water quality and loss of biodiversity in the Lake Hawassa and Shallo Wetland ecosystems.

Keywords: Basic Prati Index, Ethiopian Biological Score Index, macroinvertebrates, wetlands