Phytoplankton flora of asejire reservoir, Southwest Nigeria

Abstract

An appraisal of the current ecological status of Asejire Reservoir was carried out using the reservoir phytoplankton composition and community structure. Monthly sampling was carried out in nine selected sites for twelve months. Data were analysed using descriptive statistics, analysis of variance, Shannon-Weiner and Evenness indices. One hundred and fifty-four phytoplankton taxa were identified. Taxa dominance was in the following order: Bacillariophycea>Chlorophycea>Charophycea>Cyanophycea>Euglenophycea>Ochrophycea>Dinophyceaa. Microcystis sp. were the most abundant species followed by Anabaena sp. and Closterium sp. The riverine zone accounted for 50.8% of the total phytoplankton population. One-way analysis of variance between the zones indicated that there was a significant difference (F=11.41, df=2, p=0.0000146) in the spatial distribution among the stations. Most of the recorded phytoplankton species are cosmopolitan with the presence of the following species: Staurastrum, Closterium, Cosmarium, Anabaena, and Oscillatoria. The presence of some pollution indicator species is a cause of concern and the need to ensure holistic and effective monitoring measure is put in place to safeguard the reservoir.