Diversity of microphytes and macro invertebrates in Nsooba Stream, Kampala City

Abstract

Nsooba stream, an urban watercourse located in the North West of Kampala has undergone significant anthropogenic influence and as a result it has suffered greatly from pollution that has arisen from numerous settlements along its course hence negatively impacting the health of the stream ecosystem. A study was therefore carried out to investigate the diversity and abundance of microphytes and macro-invertebrates and how they are affected by physico-chemical parameters (i.e. temperature, dissolved oxygen, pH, flow velocity, depth and width of the stream channel) along the watercourse. Three sampling sites were selected; upstream, midstream and downstream. From each of these points, biological (microphytes and macro-invertebrates), chemical (dissolved oxygen) and physical data (pH, flow velocity, temperature, width and depth) were sampled in triplicates. Results indicated 16 genera of microphytes recorded including; Anabaena, Anacystis, Chlorella, Closterium, Euglena, Navicula, Nitzschia, Phacus, Pithophora, Schizomeris, Spirogyra, Stauroneis, Synedra, Ulothrix, Volvox, and Zygnema. Individuals of macro-invertebrates belonging to nine families were also identified and these included; Chironomidae, Psychodidae, Syriphidae, Ephyridae, Naididae, Scirtidae, Planorbidae, Coenagrionidae, and Capnidae. Water temperature, pH, depth and width increased downstream except for dissolved oxygen and flow velocity that decreased downstream. This was due to changes in water quality as a result of pollution from various anthropogenic activities such as dumping wastes directly into the stream. Thus accumulating organic matter in the water channel that is broken down resulting in an increase in stream temperature and decrease in dissolved oxygen. There was generally no significant relationship between the physico-chemical and biological parameters except for microphytes ‘Phacus’ and ‘Closterium’ whose abundance was significantly affected by 2 temperature, pH, and dissolved oxygen. However, in order to minimize pollution of streams, a distance of 30m away should be encouraged unless having obtained a written authority from the NEMA executive director according to The National Environment Act Cap 153. The National Environment (Wetlands, River Banks and Lake Shores Management) Regulations, 2000; such that wastes from the nearby settlements are not directly disposed into the watercourse.