Macroinvertebrates as bioindicators of environmental quality of wetlands of Lake Tana, Ethiopia

The present study evaluated the ecological quality of wetlands surrounding Lake Tana, Ethiopia, using aquatic macroinvertebrates as bioindicators. A total of 83 taxa were identified from 52 families and 19 orders. Biotic indices, including the Hilsenhoff Family Biotic Index (HFBI) and the Biological Monitoring Working Party (BMWP) score, were applied at the family level. Diversity metrics varied significantly between wetlands, with Zewdie Girar (ZG) showing the highest diversity and Megech River Mouth (MRM) and Gumara River Mouth (GRM) the lowest. Biotic indices and multivariate analyses classified the wetlands into three distinct pollution categories along an anthropogenic pollution gradient: Wonjeta (WO) as the least impacted; Avaj (AV), Ras Abbay (RA) and ZG as slightly to moderately polluted; and GRM and MRM as the most degraded. The Ephemeroptera, Plecoptera and Trichoptera (EPT) index confirmed cleaner conditions in AV, WO and RA. Multivariate analyses grouped wetlands into four statistical clusters along pollution gradients. Environmental factors such as salinity, ammonia, and nutrient levels influenced macroinvertebrate distribution patterns. These results confirm that macroinvertebrate communities reliably reflect wetland ecological conditions. The present study recommends integrating biological monitoring into national water quality programmes and prioritising the conservation of indigenous wetland vegetation.