Macroinvertebrate community structure and diversity in relation to environmental factors in wetlands of the lower Gilgel Abay River catchment, Ethiopia

Abstract

The influence of environmental factors on the diversity of macroinvertebrates was studied in the wetlands of the Gilgel Abay River (GAR) catchment in Ethiopia. The study was done between September 2017 and March 2018, encompassing both wet and dry seasons. Six study wetlands from the GAR catchment were selected in a targeted manner based on the surrounding land use, exposure to anthropogenic disturbances and accessibility to conduct a quantitative study. The relationships between biological and environmental variables were evaluated by using multivariate analyses. Altogether, 36 families of macroinvertebrates were identified. Macroinvertebrate diversity indices were significantly higher at less impaired sites, compared with more impaired sites. Several families of Ephemeroptera, Odonata and Trichoptera taxa, including Corduliidae, Calopterygidae, Baetidae, Aeshnidae, Polymitarcyidae, Hydropsychidae, Heptageniidae, Polycentrapodidae, Hydroptilidae and Philopotamidae were negatively correlated with organic and inorganic pollutants and human disturbances and might be considered as potential indicators of less impaired sites. Conversely, the families Chironomidae, Hirudinidae and Libellulidae were positively correlated with biological oxygen demand, ammonium and human disturbance score and negatively correlated with dissolved oxygen. Generally, results of macroinvertebrate diversity and composition in this study indicate poor ecological condition of the wetlands, particularly those adjacent to agricultural and urban areas.