Macroinvertebrate assemblages along a gradient of physicochemical characteristics in four riverine wetlands, Upper Blue Nile basin, Northwestern Ethiopia.

ABSTRACT

This study aims to examine the physicochemical variables that influence macroinvertebrate assemblages in wetlands of the Fetam River watershed. Macroinvertebrates and water quality samples were collected from 20 sampling stations across four wetlands between February and May 2022. Principal component analysis (PCA) was used to elucidate the physicochemical gradients among datasets and canonical correspondence analysis (CCA) was applied to explore the relationship between taxon assemblages and physicochemical variables. Aquatic insects such as Dytiscidae (Coleoptera), Chironomidae (Diptera), and Coenagrionidae (Odonata) were the most abundant families, and they comprised 20-80% of the macroinvertebrate communities. As demonstrated by cluster analysis, three site groups including slightly disturbed (SD), moderately disturbed (MD), and heavily disturbed (HD) sites were identified. PCA showed a clear separation of slightly disturbed sites from moderately and highly impacted sites. Differences in physicochemical variables, taxon richness and abundance, and Margalef diversity indices were observed along the SD to HD gradient. Phosphate concentration was an important predictor that influenced richness and diversity. The extracted two CCA axes of physicochemical variables accounted for 44% of the variability in macroinvertebrate assemblages. Nutrient concentration (nitrate, phosphate, and total phosphorus), conductivity, and turbidity were the main drivers of this variation. This suggested the need for sustainable wetland management intervention at the watershed level, ultimately benefiting invertebrate biodiversity.