Heavy metal accumulation and benthic foraminiferal response following the Peruvian Ventanilla crude oil spill (January 2022)

The accidental release of around 11,000 barrels of crude oil off the central Peruvian coast (11.92°S, 77.18°W) on January 15, 2022, affected ∼70 km of shoreline. This study analyzes the spatiotemporal variation of metal concentrations in intertidal and subtidal zones from October 2022 to September 2023, and their effects on benthic foraminiferal communities. Metal concentrations were found to exceed background levels established by the Peruvian Environmental Inspection Agency. Although no temporal trends were detected, spatial differences were recorded. Intertidal sites showed enhanced concentrations of V, Fe, Cr, and Mn. Notably, the site closest to the spill (Ventanilla Beach; 11.87ºS), recorded the highest concentrations of Pb, Cu, Zn, and As. In the subtidal zone, concentrations increased with water depth and reduced hydrodynamic conditions. The more sheltered site (Punta Mulatos; 11.76ºS) had higher Ni, Pb, Cu, Cd, Zn, and As levels compared to the more dynamic site (Bahía Blanca; 11.83ºS). Furthermore, a contribution associated with natural rock leaching was detected. These findings suggest that the spill's influence on metal concentration is amplified by low hydrodynamics, low oxygen, high productivity and riverine inputs. Dominant benthic foraminiferal taxa, typical of oxygen-poor environments, were associated with enhanced Cd, Cu, Ni, Cr, and Pb. However, isolating spill effects is challenging due to natural species tolerance and concurrent El Niño conditions affecting oxygen levels and organic matter fluxes. Finally, 18 months after the spill, heavy metals persist in both environments, underscoring the need for long-term monitoring and mitigation.