ABSTRACT

The study identified the effect of abattoir waste on the abundance and distribution of plankton of the increasingly abattoir activities in Imo River, Oyigbo, a Delta area of Nigeria, as indicators of the health of the aquatic ecosystem. Plankton samples were collected once monthly for 10 months (January - October 2017).  Result showed monthly variations of Physico-Chemical parameters. Means of monthly values of pH ranges between 6.00-7.12, temperature ranged between 18 – 24⁰C, and electrical conductivity was between 273.33µs/cm – 540.00µs/cm . Dissolve oxygen (DO), Dissolved solid (DS) and Biological oxygen demand (BOD) Means  of monthly values ranges between 3.53±0.03 mg/l – 6.00±0.31mg/l, 103.67±5.78mg/l - 131.00±12.01mg/l, and 5.10±0.10mg/l – 6.83±0.20mg/l respectively. Four Phytoplankton phyla were recorded, they were dominated by Chlorophyceae made up of Scenedesmus sp, Spirogyra sp, Ulothrix sp, Volvox sp, with Spirogyra sp in abundance in station 1 and a decrease of the specie through station three, followed by Cyanophyceae made up of Microcystis sp, Oscillatoria sp, Gomphosphaeria sp, Anabaena sp and dominated by Microcystis sp in station one (Upstream of the river) as it reduces significantly across other stations followed by Euglenophyceae with only Euglena sp recorded across all stations having its highest abundance in station one and Baccillariophyceae which comprises of Cyclotella sp, Cymbella sp, Diatomella sp with its dominance at station (3) three and Cyclotella sp having highest abundance. The Zooplankton of the River were made up of Protozoa: (Paramecium sp, Pelomyxa sp, Acanthometron sp) having its abundance in station three, Rotifers (Keratella sp, Branchionus sp, Monostyla sp, Euclanis sp) and Cladocera(Daphnia sp, Microcyclop sp, Bosmina sp).   Correlation matrix showed that there were significant correlation between Phytoplankton, Zooplankton and Physico-Chemical parameters. Plankton abundance peaked in station 1(842 organisms/ml) and was least in station 3. The dominating presence of Chlorophyceae shows gradual deterioration of the water quality. This could be as a result of abattoir activities, such as the wastes washed into  the river. The low abundance and distribution recorded could be attributed to growth-limiting perturbations created by ongoing abattoir activities in water columns.