Multimetric index of macro-invertebrates for ecological assessment of the Boyo wetland in the Central Rift Valley region of Ethiopia

Wetlands are invaluable places with a distinct ecosystem that shares the features of both aquatic and terrestrial ecosystems. Macroinvertebrates are vital components of wetland ecosystems. Therefore, this study aimed to assess the composition and distribution of macroinvertebrates of the Boyo Weland in relation to physicochemical parameters. Sites that can be used as potential reference sites were established using habitat quality assessment. A sample of water quality and macroinvertebrates was collected at each predefined sampling site during November and December of 2023 and January, February, and March of 2024. A total of 1,112 macroinvertebrates were collected from 10 orders and 33 families. The majority are generally pollution-tolerant families of the order Coleoptera (32.3%), Hemiptera (26.4%), Gastropoda (6%), and Diptera (2.6%). Redundancy analysis (RDA) was employed to evaluate the relationship between macroinvertebrate metrics and environmental variables. The results of RDA revealed that high taxa richness and the presence of Ephemeroptera, Plecoptera, and Trichoptera (EPT) are favored by high dissolved oxygen, low electrical conductivity, and turbidity. At the study wetland, a total of twenty-one potential macroinvertebrate candidate metrics were tested for each sampling site. Only six metrics passed the necessary procedure for the final single metric development. Therefore, a multimetric index for the Boyo wetland (BMMI) was developed using six candidate metrics, which can separate between reference and test sites. The MMI indicates that the reference sites had moderate to high water quality, whereas the testing sites had poor to bad water quality. To reverse the deterioration in water quality observed in the test sites, an immediate intervention is urgently required.