An integrated study of the plankton community after four years of Fundão dam disaster.

Mining activities can affect the environment either by the tailings releasing or dams failures. The impact of the tailings can last decades and cause chronic effects due to their toxicity. The Fundão dam collapse, a relevant environmental disaster, occurred in November 2015 in Southeastern Brazil. Tailing rich in metals reached the Doce River and arrived in the Atlantic Ocean. Previous studies revealed the acute impact of the tailings in the marine planktonic community near the Doce River mouth. The current study aims to characterize the structure of planktonic assemblages in the impacted area after four years of the disaster. Sampling occurred in November 2018, January, April, and July 2019 at 32 stations located at the marine coastal area near the Doce River mouth. Our study detected high metal concentrations in the surface waters during January 2019, when the lowest diversity and abundance of phytoplankton, lowest zooplankton diversity, and low ichthyoplankton abundance were recorded. The zooplanktonic community was structured by environmental parameters and ichthyoplankton assemblages in November 2018, January and April 2019. Nutrients and metals, mainly iron from the tailing carried by the Doce River waters to the marine environment changed the plankton community, confirming the impact of the Fundão Dam collapse in the coastal area near the Doce River mouth. The phytoplankton community, influenced by the nutrients and to a lesser extent metals concentrations, was not decisive in the zooplankton community structure. The environmental variability was driven by the meteoceanographic conditions and the Doce River flow. There was a high correlation between the zooplanktonic community and ichthyoplanktonic assemblage and the environmental factors and metals. These relations indicate the impact of the tailings from the collapse of the Fundão Dam on these communities, even after four years of the Mariana disaster.

Marine zooplankton dynamics after a major mining dam rupture in the Doce River, southeastern Brazil: Rapid response to a changing environment.

Zooplankton were sampled five days after the tailings from the Samarco dam rupture reached the ocean in the coastal region at the mouth of the Doce River. This was one of the largest environmental disasters in Brazilian history, and the impacts on the marine biota are not yet fully understood. This study aimed to evaluate the zooplankton community short term responses to the metal enrichment after the tailings reached the coastal region in different scenarios. Our results showed an acute impact on the zooplankton community, which peaked in abundance (222,958.60 ind/m3) and decreased in diversity (H' = 1.23) near the river mouth. Two copepod species, Parvocalanus sp. and Oithona nana, composed up to 61% of the total abundance and they were correlated with concentrations of Fe, Pb, Cu and Zn in particulate fraction. These species feed opportunistically on nanophytoplankton, which dominated the autotroph community, possibly in response to the iron enrichment caused by the mud flow. A shift on zooplankton species composition was also observed. During the first three days, we found the presence of oceanic species in the 20 and 30 m isobaths during an incomplete upwelling event, which directly correlated with the presence of Calanoides carinatus. However, only three days later, following a cold front passage and consequent increase of water turbidity, those species were already absent, and the zooplankton community was significantly altered (PERMANOVA, df = 1, pseudo-F = 9.2247, p = .001). Zooplankton responded quickly to the environmental changes detected during our sampling period and proved to be key factors in costal monitoring, especially in dynamic oceanographic areas such as the Doce River coastal region.