Assessment of anthropogenic metal pollution in Bagnoli (Gulf of Naples) through changes in foraminiferal assemblages and shell chemistry

Chemical pollutants, such as heavy metals, are a major threat to marine ecology and biodiversity in the Mediterranean Sea. The Gulf of Naples plays a crucial role in risk assessment and mitigation of waste contamination in the area, as severe anthropogenic pressure originates from local urban and industrial areas and intense maritime traffic. The now defunct ILVA steel plant in Bagnoli, constructed between 1905 and 1910, was a leading contributor of metal pollution (such as iron, lead, and zinc) in the Gulf of Naples until its shutdown in 1990. In order to evaluate the potentially long-lasting impact of this industrial activity on local benthic foraminiferal communities (living and dead) and the incorporation of metals in benthic foraminifera shells, a contaminated sediment sample near the former steel plant (Site A) was analyzed, and the results were compared to a less impacted sample approximately 1.85 km apart (Site B); inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES) revealed exceptionally high levels of metals in the sediment samples taken in close proximity to the former steel plant. Foraminifera community analysis via stereo microscopy and scanning electron microscopy (SEM) concluded slightly lower biodiversity indices and a lower abundance of living foraminifera in the sediment close to the steel plant. Energy-dispersive X-ray spectroscopy (EDX) was utilized to determine concentrations of iron within foraminiferal tests and established that all analyzed specimens from sampling site A had elevated quantities of iron in their tests, compared to individuals from sampling site B. Based on the findings of this investigation, the metal pollution emitted by the former steel mill is still impacting foraminiferal assemblages and individuals to this day. However, the complex interactions of anthropogenic toxins, benthic microorganisms, and the environment are not fully unraveled yet and require further analysis.