Vol. 4, Issue 2, Part B (2022)

The plankton diversity of Oriyanrin lagoon, Ogun State, was sampled from February to September 2019. Plankton net was used to collect samples for plankton analysis. A plankton analysis per ml was carried out in the laboratory with the help of a binocular microscope. Results were presented using inferential and descriptive statistics, while diversity data was analyzed using diversity software. Forty taxa of plankton were encountered. Phytoplankton consisted of three families namely; Cyanobacteria, Bacillariophyceae and Rhodophyceae. Three groups of zooplankton encountered were Protozoa, Xanthophyceae and Desmidaceae. The plankton diversity of Oriyanrin lagoon, the system was high with a Simpson diversity index of 0.97, low dominance (0.03), and high evenness (0.94). The high value of plankton taxa and the number of individuals was an indication of a good aquatic environment. This ecological system should be maintained, which supports high plankton diversity, and its pollution should be discouraged to continue providing a healthy habitat for its aquatic inhabitants.