Anthropogenic impact due to mining from a sedimentary record of a marine coastal zone (SW Sardinia, Italy)

Mining is one of the most impacting human activities on both terrestrial and marine environments due to the processing of ores and consequent production of large amount of waste materials. This research considered a sediment core from the marine coastal zone of the former Sulcis-Iglesiente mining district (SW Sardinia, Italy) where changes of benthic foraminiferal assemblages were studied along the last 4500 years and assessed in relation with grain size and heavy metals by means of multivariate statistical techniques. While sediment texture did not record changes of the depositional environment, foraminiferal assemblages showed modification correlated with the increasing pollution load due to mining. Although two epifaunal grazing species, Rosalina bradyi and Asterigerinata mamilla, proved to be resilient to heavy metal contamination, a faunal change characterized the transition from ancient unpolluted sediments to younger polluted ones. It consisted in the increase of free grazing taxa at the expense of permanently attached suspension feeders, associated to a general decline of the absolute abundance. Then, absolute foraminiferal abundance was demonstrated to be reliable proxy for assessment of environmental status in heavy metal polluted environments. This research suggests the usefulness of creating a specific index based on absolute abundance for the application of benthic foraminifera in the environmental assessment of metal polluted marine areas.