Benthic Foraminifera as Indicators of Oil-Induced Stress in the Imo River Estuary (Niger Delta, Nigeria)

Abstract

The Niger Delta is one of the most polluted deltaic ecosystems globally, with decades of oil spills and leakages severely impacting aquaculture, local flora, and water quality. This study investigates the environmental health of the Imo River estuary, a primary sink for regional pollutants. Benthic foraminifera were utilized as environmental proxies due to their high abundance, rapid reproduction rates, and sensitivity to physicochemical shifts. Analysis of benthic assemblages, stable isotopes, and heavy metal concentrations revealed an ecosystem under extreme physiological stress, characterized by significantly low species diversity and a dominance of stress-tolerant taxa. The presence of negative δ13C values indicates significant deterioration in the quality of organic matter, alongside a notable increase in acidity. This has a detrimental effect on calcareous benthic foraminifera due to lower pH levels. Our findings provide a critical baseline for evaluating the long-term impact of oil contamination and offer a quantitative metric to assess the efficacy of ongoing remediation and clean-up efforts in the region.