Food web structure of fish communities of Doce River, 5 years after the Fundão dam failure.

The rupture of the Fundão dam is considered the largest mining failure in history, which had a particularly detrimental impact on fish populations, as the mud from the ore tailings significantly altered the water quality and habitat of Doce River basin. This study aimed to assess the trophic structure of fish communities in areas impacted and not impacted by the dam rupture in the Doce River basin. To evaluate the food web structure, community-wide trophic niche, and trophic positions of fish, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were utilized across ten sites (seven impacted and three control). In general, fish appeared to assimilate resources such as invertebrates, algae, and periphyton, although the importance of each resource varied among sites. The site closest to the dam rupture exhibited a more simplified trophic structure compared to the control sites and those nearer the river mouth. In this site, most fish species occupied a similar trophic position. Trophic niches also exhibited the greatest dissimilarity between the site closest to the dam failure and those farther away from it, with an expansion of trophic niche breadth observed with an increase in the distance from the dam rupture. Our study provided valuable insights into the trophic structure of fish communities within the Doce River basin, shedding light on the trophic ecology of the 59 fish species investigated. We also emphasize the importance of our study for future assessments of ore tailings dam failure disasters and evaluating the effectiveness of mitigation measures for Doce River basin recovery.

Impacts of the Samarco Tailing Dam Collapse on Metals and Arsenic Concentration in Freshwater Fish Muscle from Doce River, Southeastern Brazil.

On November 2015, Samarco tailings dam in Mariana, Minas Gerais, Brazil, collapsed, releasing 62 million tons of tailings that advanced through 668 km of the Doce River and adjacent floodplain. Although the collapse was the worst environmental disaster in Brazil, little is known about its consequences to aquatic biota. Here we evaluate the effects of the tailings mudflow on metal and As concentration in fish and how concentration correlates with water and fish characteristics. We quantified semitotal amounts of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in fish muscle tissue using inductively coupled plasma mass spectrometry (ICP-MS) in 255 individuals (34 species) sampled in unaffected and affected areas along the Doce River basin. Arsenic and Hg were higher in fish from affected sites, likely due to turbulent mixing of previously sedimented material by the giant tailings wave. Silver and Zn concentrations were higher in unaffected sites. Arsenic concentration in Geophagus brasiliensis decreased with increasing fish weight. Copper and Zn decreased with increasing fish weight considering the whole assembly of fish. The tailings mudflow increased water conductivity, and conductivity increased Al concentration in fish, so we expected a larger Al concentration in fishes from affected sites. However, the observed Al concentration in fishes from affected sites was lower than expected by water conductivity. Thus, the tailings mudflow reduced Al uptake or accumulation in fishes. Mercury decreased with increasing water conductivity in both unaffected and affected sites considering all species and in G. brasiliensis alone. Despite the relatively low concentration range of metals and As found in fish, fishes from sites affected by the Fe ore tailings mudflow showed higher As and Hg concentration, compared to fishes from unaffected sites. The higher As and Hg in affected sites require further detailed monitoring to ensure safeguards of human health by fishing activity along the Doce River. Integr Environ Assess Manag 2020;16:622-630. © 2020 SETAC.

Em novembro de 2015, a barragem de rejeitos da Samarco em Mariana, MG, Brasil, rompeu, liberando 62 milhões de toneladas de rejeitos de minério de ferro que avançaram por 668 km do rio Doce e planície adjacente. Embora este tenha sido considerado o pior desastre ambiental do país, pouco se sabe sobre as consequências da liberação do fluxo de lama para a biota aquática. Aqui avaliamos os efeitos do fluxo de lama de rejeitos sobre a bioacumulação de metais e arsênio em várias espécies de peixes coletadas na bacia do rio Doce e como a bioacumulação se correlaciona com as características da água e dos peixes. Quantificamos as quantidades semitotais de Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb e Zn no tecido muscular de peixes usando ICP-MS em um total de 255 indivíduos (representando 34 espécies), amostrados em locais não afetados e afetados ao longo da bacia do rio Doce. As concentrações de As e Hg foram maiores nos peixes dos locais afetados, provavelmente devido à mistura turbulenta de material previamente sedimentado pela onda gigante de rejeitos. As concentrações de Ag e Zn foram maiores nos peixes de locais não afetados. A concentração de As na espécie mais abundante nos locais não afetados e afetados (Geophagus brasiliensis) diminuiu com o aumento do peso dos peixes. A concentração de Cu e Zn diminuiu com o aumento do peso dos peixes, considerando toda a assembleia de espécies. O fluxo de lama de rejeitos aumentou a condutividade da água e a condutividade aumentou a concentração de Al nos peixes, portanto esperávamos uma maior concentração de Al nos peixes de locais afetados. No entanto, a concentração de Al observada nos peixes de locais afetados foi menor do que o esperado pela condutividade da água. Assim, o fluxo de lama de rejeitos reduziu a assimilação ou o acúmulo de Al nos peixes. O mercúrio diminuiu com o aumento da condutividade da água nos locais não afetados e afetados, considerando todas as espécies e também dentro de G. brasiliensis. Apesar da faixa de concentração relativamente baixa de metais nos peixes, os peixes de locais afetados pelo fluxo de lama de rejeitos de minério de ferro apresentaram maior concentração de As e Hg, em comparação com peixes de locais não afetados. A maior concentração de As e Hg nos locais afetados requer um monitoramento mais detalhado para garantir segurança alimentar em relação à atividade pesqueira ao longo do rio Doce. Integr Environ Assess Manag 2020;16:622-630.