Diatoms as an Indicator of Water Quality in the Kuils River, Western Cape, South Africa

Rivers are crucial hydrological cycle components, supporting ecosystems and human activities. Managing and protecting river water quality is essential. Diatoms, microscopic algae, are widespread and sensitive to changes in water quality, making them effective bioindicators. This study focused on the Kuils River in the Western Cape, South Africa, where diatom sampling was conducted at four sites. Their communities are affected by different physicochemical parameters, such as changes in pH, salinisation, eutrophication, and organic enrichment. A total of 98 diatom species were identified. The Omnidia software was used to calculate the Generic Diatom Index, Specific Pollution Index, and Trophic Diatom Index. Historical physicochemical data from the Department of Water and Sanitation provided a reference for comparing diatom communities. The results showed clear signs of pollution, as shifts in diatom species composition were observed. Pollu-tion-tolerant species like the Nitzchia palea, Navicula viridula, Eunotia bilunaris, and Fragilaria ulna dominated, while less pollution-tolerant species like Gomphonema parvulum and Cyclotella meneghiniana were less abundant. Both diatom indices and physicochemical data indicated poor water quality in the Kuils River. The study concludes that diatoms are a valuable tool for biomonitoring river water quality and recommends their use alongside traditional physicochemical methods for future assessments of river sys-tems.