Diatom Checklist, Composition and Abundance of a Lotic Aquatic Ecosystem in Edo State, Southern Nigeria

The diatoms of Osse River, Edo State, were studied at monthly intervals for 16 months (January 2003–April 2004) across five stations. Stations 1, 2 and 3 were freshwater stations while stations 4 and 5 were brackish environments. Phytoplankton samples for qualitative analysis were collected monthly in the open water using a plankton net of 55 µm mesh size tied unto a motorized boat and towed at low speed at all stations each time for 5minutes. Samples for quantitative analysis were collected using a 10 litre bucket to take River water into 55 µm mesh size plankton net which was held in a vertical position five times making 50 litres. Net catches of the different samples were preserved in 4% formalin solution in well labelled plastic containers and analysed in the phycology laboratory, University of Benin, Benin City. Samples for physico-chemical analysis were taken from the open water using a 1 litre plastic container in each station and taken to the chemistry division of Nigeria Institute for Oil Palm Research (NIFOR) for analysis using standard methods. The aim of this work was to investigate the diatoms of Osse River as well as their composition and abundance. A total of 53 diatom species belonging to 26 genera were recorded. Osse River diatoms were observed to be rich and diverse with a significant difference in the dry and wet season compositions. Results of the physico-chemical parameters show that apart from pH which showed no significant difference (P>0.05), there was significant difference (P<0.05) among the parameters studied. Correlation analysis of Bacillariophyceae with physico-chemical parameters shows significant correlation with pH, electrical conductivity and silica. Coscinodiscus centralis Ehrenberg was the most abundant species in the study. Stations 4 and 5 accounted for more diatoms in the study. This is a pioneer investigation reported for diatoms of Osse River.