Studies on the distribution and abundance of plankton in Awba stream and reservoir, University of Ibadan

Abstract

Studies were carried out on the distribution and abundance of plankton in Awba stream and reservoir, University of Ibadan over a period of four months between November 2011 and February 2012. Studies were carried out at four selected stations comprising station 1 as the entry point of the stream into the University, which also served as the control, station 2 receiving sewage, station 3 downstream along the stream and at a point along Awba Reservoir serving as station 4. 1 ml aliquot of each plankton sample from the study stations were examined under a binocular microscope while identification of the plankton was carried out using standard textbooks. The results of the phytoplankton indicated the absence of Microcystis flos-aquae , Agmenellum and Oscillatoria limnetica in station 1 while members of the family bacillariophyceae appeared at all stations. All species of chlorophyceae family except Spirogyra were peculiarly absent at station 2. Other phytoplankton representatives at this point (station 2) included Microcystis , Anabaena , Oscillatoria and Melosira . Paramecium was the only zooplankton group that was absent in station 1 but the only species presented in station 2. This station also revealed the lowest diversity indices and very low or no Jaccards coefficient of similarity with the other stations. The overall differences observed in the abundance, species richness, Margalef and Shannon-Wiener indices of diversity of plankton in the study reveal self purification or recovery downstream from the effluent discharge.