Assessment of the quality of Kinawataka stream in Nakawa division, Kampala using Benthic macroinvertebrates as Bioindicators

Abstract

Aquatic macroinvertebrates are a faunal group that respond fast to water quality stressors, such as effluents from anthropogenic activities which affect aquatic environments, hence good indicators of pollution used to monitor stream health. Kinawataka stream is susceptible to the effects of urbanization, industrialization and other anthropogenic activities resulting from rapid population growth linked to rural-urban migrations thus it has undergone severe ecological degradation. There was need to monitor and assess water quality in the stream using macroinvertebrates as bioindicators to establish its status. Sampling was done for a period of two months, December 2021 and January 2022. Seven sampling sites categorized into (upstream, midstream and downstream), each approximately 250m apart were used to collect the macroinvertebrates. Modified sampling protocol adopted from the Tanzania River Scoring System (TARISS) approach, (Kaaya et al., 2015) was used for the study; and the data analysis of macroinvertebrates followed Ochieng (2021). Seven families of aquatic macroinvertebrates were found including: Acanthobdellidae, Bulinidae, Chironomidae, Lumbriculidae, Planorbidae, Hydrophilidae and Psychoda. The results show that macroinvertebrates were spatially distributed among the different sites along Kinawataka stream and the diversity indices indicated that site 2 had the highest diversity (H′) = 0.7 and evenness (E) = 0.3, respectively compared to other sites. The abundance was higher at site 3 and lowest at site 4. Family Lumbriculidae was the most abundant, while the least abundant families were Planorbidae and Hydrophilidae. The pollution variations at each site depended on the different anthropogenic activities from both point and non-point sources such as industrial effluents and municipal waste discharge and therefore, the low diversity was attributed to the various anthropogenic activities including urbanization, industrialization and less vegetation cover. The presence of highly tolerant aquatic macroinvertebrates and absence of sensitive macroinvertebrates to pollution in all the sites indicates that Kinawataka stream was seriously affected by pollution as a result of effluents from anthropogenic activities. Therefore, effective management strategies have to be developed to support urban stream conservation through proper treatment of effluents from anthropogenic activities before they are released into the stream, restoration of degraded wetlands, carrying out more research on stream health and formulating better policies regarding conservation of aquatic environments by policy makers.