Long-term impacts on estuarine benthic assemblages 4.2 years after a mine tailing spill in SE Brazil

Abstract

The Rio Doce estuary was critically impacted in 2015 by the world’s largest mining tailing spill, with still unclear long-term effects. Here we present a long-term (2015 to 2020) assessment of estuarine benthic assemblages, where Annelida and Mollusca were dominant (52.6% and 26.3%, respectively). Our results demonstrated that the density and richness of benthic taxa decreased in response to an increase in potentially toxic elements concentrations, suggesting a chronic pollution effect that lasted for at least 4.2 years in the estuary. Our data demonstrated that despite the decline in sediment potentially toxic elements concentration over time, there was a continued low habitat quality for the benthic fauna characterized by a reduction of 96% on macroinvertebrate density and 48% on species richness. The long-term impacts on benthic macrofauna highlight that water quality levels can misguide impact assessment programs, and reveal that mine tailings impacts persist for many years in estuarine ecosystems.