Bio-evaluation of the Ecological Health Status of Petroleum Effluent Receiving Water from Eleme River, Nigeria

Abstract

The ecological Health Status of Eleme River receiving treated petroleum effluent wastes from Eleme Petroleum Refinery Company was evaluated using a combined approach of biological methods; petroleum effluent bioindicators, functional diversity and community assemblage metrics, and physicochemical methods; TPH, nutrients, turbidity, DO, pH, Heavy metals, and total dissolved solids analysis. This was carried out, knowing that effluent discharges change the biodiversity of aquatic macro invertebrates, particularly insects, reduce their functional roles, and change their physicochemical requirements. The River was divided into 3 stations; upstream (receiving point), midstream, and downstream, with each station further divided into 3 sampling points. The collection of macro invertebrates was done, using handnets and Eckman’s grab from floating vegetation, logs, and sediments. The samples were placed in a 4-L bucket containing 70% ethanol and 5% glycerin and transported to the Entomology Research Laboratory, Department of Animal and Environmental Biology, the University of Port Harcourt for sorting and identification. Composite water samples were taken for analyses of physicochemical properties using standard devices and methods. Results obtained indicated that out of 18 species encountered, 12 were monitor indicators, 5 were facultative tolerant indicators and none were sensitive indicators. Five species (taxa) occurred at both up and mid-streams and seven occurred downstream. Daphnia barbata and macrobranchium sp., occurred commonly in the three stations. The insect indicators encountered were seven, all of the downstream, and were dominated by insects belonging to the order: Hemiptera. Three functional groups; Detritivorous, collector-herbivorous, and predators were encountered with detritivorous being dominant. The TPH, nitrate, phosphate, copper, and nickel concentrations in all sampling stations were above the intervention limits of the World Health Organization (WHO). Concentrations of physicochemical properties except DO and pH were higher downstream. Shannon-Weiner index showed that the absence of species belonging to Ephemeroptera, Plecoptera, and Trichoptera in all stations indicated that Eleme River has a poor ecological health status.