Comparative ecotoxicological study on the current status of artisanal crude oil contaminated mangrove swamps in Rivers State, Southern Nigeria

Abstract

The rise in illegal crude oil theft and refining in the southern Niger Delta region of Nigeria, especially in Rivers State, has led to significant environmental damage to aquatic ecosystems. A study was carried out to assess the impact of crude oil bunkering on aquatic environments and fish samples from Oproama, Sama-Naguakiri, and Abalama over six months. Findings revealed that Oproama had the highest levels of biological oxygen demand (3.60 ± 0.79 mg/L), electrical conductivity (34.07 ± 3.62 μS/cm), total dissolved solids (28.17 ± 3.77 mg/L), and temperature (29.50 ± 0.74 °C). In contrast, Sama-Naguakiri recorded the highest pH (6.72 ± 0.14) and dissolved oxygen (3.35 ± 0.11 mg/L). Though minor variances were noted between Sama-Naguakiri and Abalama, a significant difference (P < 0.05) was observed between these areas and Oproama. Importantly, all measured values adhered to WHO/FAO standards. Analysis of potentially harmful metals in sediment and water indicated notable distinctions among the three sites, with Sama-Naguakiri exhibiting the highest levels of Zn (114.5 ± 1.5 mg/kg), Cu (237.8 ± 0.9 mg/kg), Pb (3.6 ± 1.2 mg/kg), and Cd (1.1 ± 0.4 mg/kg). Conversely, Abalama showed the lowest zinc (105.2 ± 1.5 mg/kg) and lead (2.4 ± 0.5 mg/kg) concentrations, while Oproama displayed the lowest copper level (0.8 ± 0.3 mg/kg). The concentrations of heavy metals in the water, sediment, and fish surpassed the permissible limits established by NESREA, the EPA, and WHO, except for arsenic. The presence of heavy metals in this region could pose significant ecological and health hazards, underscoring the urgency for immediate remedial measures to safeguard the environment and this fish-dependent community.