ABSTRACT

 This study was undertaken to assess the response of River Ogba phytoplankton to nutrient enrichment. Samples were collected in River Ogba on the 14th day of April, 2023. Different types of samples, such as water and periphyton were collected. Two sets of experiments were set-up one with natural phytoplankton population and the other with introduced phytoplankton. Two test algae namely Chlorella vulgaris, Scenedesmus arcuatus were used separately for innoculating the introduced phytoplankton. Growth response was determined using spectrophotometer at 750nm for 14 days, at two days interval. Results showed that N+P treatment had higher growth than N, P, and control. The periphyton composition of the river comprised only one division of Chlorophyta with four taxa (Hyalotheca undulata, ulothrix sp, ulothrix tenuissima and Spirogyra dubia). Growth response showed that nutrient enrichment was favourable in Chlorella vulgaris and Indigenous phytoplankton while Scenedesmus arcuatus were not favourable to the nutrient enrichment. The physical and chemical parameters indicated that Ogba River was less polluted indicating that results were within tolerance limits for aquatic life. It was concluded that, since phytoplankton are beneficial to human health, and the aquatic ecosystem their response of nutrient enrichment is crucial in controlling phytoplankton bloom dynamics in river Ogba.