Zooplankton Community Responses in a Perturbed Tropical Stream in the Niger Delta, Nigeria

摘要

The effect of abattoir wastes and other anthropogenic activities on the distribution and abundance of zooplanktonand environmental variables were investigated in Orogodo River, southern Nigeria. Samples of zooplankton were collectedfor a period of six months from three stations, representing upstream of the river course, effluent discharge pointand downstream of the river course. A combined total of 79 species of zooplankton were encountered in the study. Station1 recorded the highest number (78 species), station 2 with 22 taxa and station 3 with 72 representative taxa, showing recoveryin terms of diversity and abundance of zooplankton. Rotifers of the order Bdelloidea dominated all the stations andwere relatively high in station 2 indicating their tolerance to a wide range of impact. Generally, the cladocerans wereabundant at all stations. However, Moina micrura, and Thermocylops neglectus were the only members of this group recordedin station 2. The low fauna diversity experienced in station 2 throughout the period of sampling showed strongevidence of impact arising from the abattoir waste discharge and heavy human activities at that station. Local environmentalconditions (i.e. Temperature, flow velocity, depth, dissolved oxygen, alkalinity and conductivity) accounted for69% of variation in zooplankton assemblages using canonical correspondence analysis (CCA). Seasonal trends inzooplankton community composition were also related to changes in environmental characteristics of the river. Our resultsindicate that the changing water quality status of the Orogodo River affected the zooplankton diversity and abundanceand such measure could be used as a biomonitoring tool to determine the ecological health of the river.