Epilithic Diatoms as Bioindicators of Water Quality in River Njoro and Kamweti, Kenya

This study used diatoms as bioindicators to assess water quality and ecological status in River Njoro and Kamweti. Physicochemical parameters of both rivers were statistically significantly different (P < 0.05). The study identified 27 diatom species across eight classes, with 25 taxa common to both rivers. However, Eunotia exigua and Amphora libyca were found only in River Kamweti. Diatom genera tolerant to pollution, particularly Gomphonema and Nitzschia were abundant in the River Njoro. Conversely, there were greater numbers and higher diversity of diatom species in the River Kamweti, which suggests that ecological conditions in River Kamweti are better than in the River Njoro. Overall, diatom abundance increased as you go downstream in both rivers. This reflects the cumulative impacts of activities along the river continuum. In addition, diatom indices Trophic Diatom Index (TDI), Diatom Pollution Sensitivity (DPS), and Saprobic Index (SI),also increased, in a downstream direction, with higher values in the River Njoro, which is likely due to increased nutrient loads and organic pollution that's causing a shift to assemblages that are less sensitive to pollution. Therefore, this study provides baseline information for sustainable management and conservation of freshwater resources in Kenya.