Distribution of Hydrocarbon-Utilising Bacteria and Fungi, Faecal Contamination and Associated Human Health Risk in Soil, Sediment and Surface Water of Eagle Island, Port Harcourt, Niger Delta, Nigeria

Abstract

Peri-urban creek margins in the Niger Delta are exposed to both petroleum-derived contamination and domestic waste, but comparative information on microbial responses across soil, sediment and surface water remains limited. This study characterised microbial populations, hydrocarbon-utilising fractions, physicochemical conditions, faecal contamination and associated non-carcinogenic health risk at Eagle Island, Port Harcourt. Samples were collected from two soil stations, one intertidal sediment station and two surface-water stations and analysed using culture-based microbiological methods, physicochemical measurements, contamination and water-quality indices, and health-risk assessment. Total heterotrophic bacterial counts were 2.70×10⁵–7.00×10⁵ CFU g⁻¹ in soil, 4.00×10⁵ CFU g⁻¹ in sediment and 6.80×10³–1.20×10⁴ CFU mL⁻¹ in water. Hydrocarbon-utilising bacteria represented 0.010–0.033% of heterotrophs in the solid matrices and 0.250–0.588% in water, while hydrocarbon-utilising fungi represented 9.5–12.5% in the solid matrices and 30.4–100.0% in water. Faecal coliforms were detected at all stations. Total hydrocarbon content ranged from 131.7 to 345.0 ppm in solids and from 12.7 to 20.0 mg L⁻¹ in water. Dissolved oxygen was 2.50–3.27 mg L⁻¹, and Water Quality Index values of 118.9–131.6 classified both water stations as unsuitable for drinking. Hazard indices remained below unity for soil and sediment contact but exceeded unity under several water-exposure scenarios. The findings indicate strong matrix dependence in the culturable hydrocarbon-utilising fraction and identify concurrent hydrocarbon, faecal and oxygen-related water-quality concerns at Eagle Island.