Phytoplankton Community Responses in A Perturbed Tropical Stream in the Niger Delta

Abstract

The effect of abattoir wastes and other anthropogenic activities on the distribution and abundance of phytoplankton and environmental variables were investigated in River Orogodo, southern Nigeria. Samples of phytoplankton were collected monthly from three stations designated as station 1 (upstream of the river course), station 2 (effluent discharge point) and station 3 (downstream of the river course) for a period of six months. A combined total of 46 species of phytoplankton were encountered in the study. Station 1 recorded a total of 45 species, station 2 with 18 taxa and station 3 with 42 representative species, showing recovery in terms of diversity and density of phytoplankton. The order of dominance in the river was Bacillariophyceae > Chlorophyceae >Cyanophyceae > Euglenophyceae. The blue-green algae (Cyanophyceae) were dominant in station 2 in terms of density and diversity indicating their tolerance to organic enrichment. Generally, Spirogyra, Ulothrix, Oscillatoria, and Navicula species were the preponderant species. Euglena viridis was the only member of the class Euglenophyceae recorded in the river and it occurred only sporadically in station 1. The low fauna diversity experienced in station 2 throughout the period of sampling showed strong evidence of impact arising from the abattoir waste discharge and heavy human activities at that station. Pearson correlation coefficient analysis indicated temporal trends in phytoplankton density and composition. This was related to changes in environmental characteristics of the river. Keywords: Phytoplankton, Spirogyra, Ulothrix, River Orogodo, Abattoir wastes, Environmental variables.Tropical Freshwater Biology Vol. 17 (1) 2008: pp. 37-52