Assessing the Relationship Between Macroinvertebrate Metrics and Fine Sediment Index for Ecological Biomonitoring in the Little Akaki River, Addis Ababa, Ethiopia.

Abstract

The Little Akaki River faces significant environmental challenges, including sedimentation, which may adversely affect biodiversity and aquatic ecosystems. Understanding the relationship between macroinvertebrate metrics and sediment index along this river is crucial for assessing the river's ecological health. This study aims to evaluate the relationship between macroinvertebrate metrics and sediment index along the Little Akaki River. The research was conducted across seven sampling sites on the basis of accessibility, intended use, and biotope richness from April to May 2024, employing a multi-habitat sampling methodology. Macroinvertebrates were collected from gravel, sand, mud, vegetation, riffles, and pools with a 500 μm D-frame net. A total of 5575 macroinvertebrates were collected from gravel, sand, mud, vegetation, riffles, pools, and sand and mud. With 11 orders and 32 families, 21 taxa were found at site 1, and the lowest number of taxa was recorded at site 7. Habitat quality showed a strong positive correlation with the percentage of Ephemeroptera (<i>r</i> = 0.833), the combined percentage of Ephemeroptera, Odonata, and Trichoptera (<i>r</i> = 0.880), and the Shannon diversity index (<i>r</i> = 0.939). The proportion of sediment-sensitive invertebrates index (PSI) had a positive correlation with the number of taxa, and the average score per taxa-Ethiopian biological score (ASPT-ETHbios) (<i>r</i> = 0.819 and <i>r</i> = 0.798, respectively). Most sites were heavily sedimented. The study reveals a significant correlation between PSI, habitat quality index, and macroinvertebrate metrics, providing clear evidence that sedimented sites are also heavily polluted. The causal relationship between fine sediment and pollution indicators needs to be investigated in detail.