Effects of mine tailings on aquatic macroinvertebrate structure within the first year after a major dam collapse

Context. The collapse of a tailings dam in Brumadinho (Brazil) is considered one of the largest mining disasters worldwide. The mine tailings polluted the water and sediment of the Paraopeba River downstream of the collapsed dam. The effects of the tailings on biological communities remain unknown. Aims. We evaluated the effects of the tailings dam collapse on aquatic macroinvertebrate assemblages in the Paraopeba River and highlighted a potential bioindicator for the cumulative effects of the mine tailings spill. Methods. We sampled the macroinvertebrates upstream and downstream of the collapsed dam during the first dry and wet seasons following the collapse. Key results. We found that turbidity (likely non-related to the tailings) negatively affected the macroinvertebrates' abundance, but the richness was negatively affected by the presence of the mine tailings. The riparian land use negatively affected the macroinvertebrate richness and composition. We identified Helicopsyche spp. as a bioindicator. Conclusions. We provide circumstantial evidence of the effects of mine tailings on aquatic macroinvertebrates, suggesting that it may have affected their richness and caused the loss of Helicopsyche spp. in the most affected sites.Implications We suggest that the richness and Helicopsyche spp. are potential biomonitoring tools for evaluating the effects of the tailings dam collapse on the macroinvertebrate assemblages.