Title: The response of macroinvertebrate communities to multiple stressors in the greater Kampala Metropolitan area, Uganda.

Author: Isaac Elia Ainembabazi

Supervising Institution: BOKU University, Vienna

Year: 2025

 

Abstract:

Benthic macroinvertebrates act as biological indicators of aquatic degradation due to their bottom-dwelling lifestyle and sensitivity to disturbances. This study investigated how macroinvertebrate communities respond to multiple stressors in the greater Kampala Metropolitan area, Uganda. A total of 26 sites were sampled for physico-chemical, hydromorphological parameters, substrates, and macroinvertebrates. Physicochemical parameters reliably categorized sites into highly disturbed-DS, moderately disturbed-MD, and natural sites-NN. A Kruskal-Wallis test determined significant differences. Results show highest phosphate concentration, temperature, EC, and BOD in DS. Nitrates, pH, and turbidity were highest in MD, while DO was highest in NN. No significant differences were shown by stream depth, width, flow velocity, and Hydro morphological Index of Diversity (HMID). Finer substrates dominated DS, and coarse substrates in NN. Multiple stressors led to increased abundance of pollution-tolerant taxa such as Chironomidae red and Oligochaeta in DS, while EPT taxa declined. Taxa richness of pollution-tolerant and pollution-sensitive taxa was highest in NN. The existing African biotic indices, such as SASS, TARISS, RS, and ETHbios, showed limitations due to missing taxa on their score sheets and possibly due to regional differences for which they were developed. This justifies the urgent need for a local biotic index for Uganda’s freshwater systems.

 

Keywords: Benthic macroinvertebrates, multiple stressors, hydromorphology, biomonitoring, biotic index, ecological integrity, and hydro-morphological index of Diversity.