Taxonomic Composition, Abundance and Distribution of Phytoplankton in Ifewara Reservoir, Southwestern Nigeria

ABSTRACT

The taxonomic composition, abundance and distribution of phytoplankton in Ifewara Reservoir, Southwestern Nigeria was studied for four months (February to December, 2015). Four sampling stations (designated Stations 1-4) were established along the horizontal axis of the reservoir from inflow region to the dam site end. The stations were all sampled at the marginal sides (A and C) and open water B except for Station 1 which was only at the open water. At each station, net plankton samples were collected by sieving 30 litres of water through a plankton net of 50 µm mesh size into 30 ml concentrate volume, preserved in 5% formalin solution and later treated with Lugol’s solution and reduced to 3 ml for microscope observation. Sixty-nine (69) species of phytoplankton were recorded from the four investigated sampling stations. The flora comprised 36 species of Chlorophyta consisting of 52% by composition, 17 species of Bacillariophyta consisting of 25%, 9 species of Cyanophyta consisting of 13%, two species of Dinophyta consisting of 3%, one species of Chrysophyta consisting 1%, three species of Euglenophyta consisting of 4% and one species of Charophyta consisting of 1%. The horizontal pattern of variation along the reservoir showed the highest phytoplankton abundance recorded at the inflow basin and the lowest abundance at the dam site. Also, almost all the phytoplankton groups had their highest mean abundance during the rainy season than the dry season.

Key Words:Abundance, Phytoplankton species, Ifewara Reservoir, Distribution.