Impacts of tailings of Fundão dam (Brazil) rupture on marine fish: Metals bioaccumulation and physiological responses

Effect of legacy and emerging pollutants on genome-wide methylation patterns in black hake (Merluccius polli) natural populations

Exposure to pollutants such as non-essential metals and microplastics can have harmful consequences for marine organisms. Detecting the impact of pollutants in wild populations can be especially challenging. Such environmental disturbances might prompt rapid responses in the affected organisms, generating changes in their gene expression mediated by epigenetic regulation. Here we use an epiRADseq approach to determine the effect of four non-essential metals (As, Cd, Hg, Pb) and microplastics (MP) on the methylation pattern of Benguela hake, Merluccius polli, captured in the FAO fishing area 34, along the coasts of Mauritania and Senegal. We analysed 49 hake specimens and generated 44,201 epigenetic loci. Despite moderate levels of pollution identified from tissue analysis, we found significant differentially methylated loci associated with the level of the five pollutants analysed (119 significant loci for As, 134 for Cd, 92 for Hg, 119 for Pb, and 159 for microplastics). Elevated Pb was significantly associated with a reduction in hake condition factor. Differentially methylated loci were associated with diverse pathways associated to responses for all pollutants (e.g. immune response, gene expression regulation), pointing to signs of stress within the population. It is worth noting that all pollutants were differentially methylated for a locus in NLRC3, previously associated with innate immune response in fishes. Overall, we found evidence of the effects of moderate concentration of pollutants in the methylation pattern in wild populations of M. polli.

A six-year ecotoxicological assessment of the Doce river and coastal marine areas impacted by the Fundão tailings dam failure, Brazil

Encompassing six years, 10 sampling campaigns, and more than 800 toxicity tests utilizing a range of organisms from different trophic levels as bioindicators, this study offers a comprehensive ecotoxicological assessment of the environmental impacts resulting from the Fundão dam rupture-one of Brazil's most significant environmental disasters. We employed a novel approach that integrates acute and chronic laboratory toxicity tests to establish a toxicity index classifying samples into five categories: non-toxic, slightly toxic, moderately toxic, toxic, and highly toxic, based on a toxicity value calculated by considering diverse organisms' responses. This evaluation, conducted between 2018 and 2023, spanned both dry and rainy seasons, assessing water and sediment conditions across the Doce River and the adjacent marine region near its mouth. Our findings reveal that, even years after the dam failure, the iron-enriched mine tailings continue to exert a significant impact on the water and sediment of the Doce River and its adjacent marine areas, with the most severe effects observed near the river's mouth and towards the North. Notably, sediment samples consistently exhibited higher toxicity values than water samples across sites and seasons, highlighting the role of sediments as reservoirs for contaminants. The most pronounced toxicological impacts were detected during the initial years following the disaster, with a gradual, though cautious, decrease in toxicity observed in recent campaigns. Emphasis is placed on the sensitivity of microcrustaceans, copepods, and sea urchins, which consistently demonstrated the highest sensitivity to contaminants, making them reliable bioindicators for ongoing monitoring efforts. While recent campaigns identified a gradual decrease in the toxicity index of the environmental samples, especially in the marine environment, this trend must be interpreted with caution. Continuous monitoring is essential to confirm sustained recovery, detect potential recontamination, and identify long-term sub-lethal effects that could impede the full restoration of the affected ecosystems.

Marine mesocosm system: A reliable tool for testing bioaccumulation and effects of seawater enrichment with dissolved iron in reef organisms

In 2015, a marine mesocosm facility was designed and implemented by the Coral Vivo Project in its research station (Porto Seguro, Bahia State, Brazil) to initially study the effects of global impacts, especially ocean warming and acidification, on coral reefs. However, local impacts, including seawater contamination with metal(loid)s, are considered as a major threat to coral reefs. Also, in 2015, the largest disaster involving a mining dam occurred in Brazil. Iron (Fe) mining tailings originated from the dam failure affected not only freshwater ecosystems (rivers, lakes and lagoons), but also adjacent beaches, mangroves, restingas, reefs and other marine systems. Seawater, sediments and biota were contaminated with metal(loid)s, especially Fe, arsenic (As), mercury (Hg) and manganese (Mn). Therefore, we aimed to adapt the marine mesocosm facility of the Coral Vivo Project to evaluate the bioaccumulation and biological impacts of increasing concentrations of dissolved Fe on a diversity of reef organisms. Results obtained indicate a great versatility and reliability of the marine mesocosm system for application in biological and ecological studies on the isolated effect of seawater dissolved Fe on reef organisms of different functional groups simultaneously.•Studies involving seawater enrichment with dissolved Fe can be performed using a marine mesocosm system.•The marine mesocosm is a reliable tool to study the isolated effects of metal(loid)s on reef organisms.

Effects of blood metal(loid) concentrations on genomic damages in sharks

The use of effect biomarkers has contributed to the understanding of the sublethal effects of contaminants on different organisms. However, the analysis of genotoxic markers as an indicator of organism and environmental health in sharks is underexplored. Thus, the present study investigated the relationship between the genomic damage frequency in erythrocytes and metal(loid) concentrations in whole blood of three shark species (Galeocerdo cuvier, Negaprion brevirostris and Ginglymostoma cirratum), taking into account climatic seasonality. The results showed that G. cuvier, an apex predator, presented the highest total erythrocyte genomic damage frequencies together with the highest mean whole blood concentrations of Al, Cd, Cr, Fe, Mn, Ni, Pb and Zn. The shark N. brevirostris also presented high levels of metal(loid), indicating a greater susceptibility to these contaminants in species that preferentially feed on fish. In contrast, G. cirratum, a mesopredator, presented the lowest erythrocyte damage frequencies and whole blood metal(loid) concentrations. The presence of micronuclei was the most responsive biomarker, and Al, As and Zn had an important effect on the genomic damage frequencies for all species evaluated. Zn concentration influenced the binucleated cells frequencies and Al concentration had an effect on the total damage and micronuclei frequencies in G. cuvier and N. brevirostris. Binucleated cells and blebbed nuclei frequencies were affected by As concentration, especially in G. cirratum, while showing a strong and positive correlation with most of the metals analyzed. Nonetheless, baseline levels of metal(loid) blood concentrations and erythrocyte genomic damage frequencies in sharks have not yet been established. Therefore, minimum risk levels of blood contaminants concentrations on the health of these animals have also not been determined. However, the high genomic instability observed in sharks is of concern considering the current health status of these animals, as well as the quality of the environment studied.

Metal tolerance in enterococci isolated from seabirds in Abrolhos Archipelago, Brazil: Evaluating their role as bioindicators of marine pollution

Microbiota exposed to pollution provide insights into host physiology and ecosystem disruption. This study evaluated Enterococcus spp. tolerant to arsenic (As), copper (Cu), and mercury (Hg) from red-billed tropicbirds (Phaethon aethereus) and brown boobies (Sula leucogaster), which previously showed these metals in their blood and feathers, and their potential use as bioindicators of metal contamination. Enterococcus casseliflavus (47.9 %), E. faecalis (34.1 %), E. hirae (11.7 %), and E. faecium (5.3 %) were identified. Both seabird species had a high incidence of As-tolerant bacteria (84.0 %), with 40.4 % of these strains containing As efflux system genes (arsA_I and arsA_II). Cu efflux pump gene (tcrB) was detected in 30.9 % of strains, while Hg reductase genes (mer) were not found. As- and Cu-tolerance in enterococci observed in this study underlines their potential as bioindicators in metal-polluted marine environments. Further research may elucidate the role of these metal-tolerant enterococci in seabird gut and their adaptability to polluted environments.

Major recent failures in Brazilian mine waste containment facilities, current cases of maximum emergency level and imminent risk of rupture, and a brief sustainability analysis

Waste is the materials left over after the processing of ores. Significant disasters involving waste disposal structures have occurred in Brazil in recent years and caused severe damage by contaminating soil, rivers and coastal areas, destroying native fauna and flora, interrupting the water supply and compromising its potability, putting the population's health, livelihoods and economy at risk, as well as causing 289 irreparable human deaths. Regulatory laws have become stricter, and since 2019, after the tailings dam tragedies occurred in 2015 and 2019 in Mariana and Brumadinho, in Minas Gerais, the operation of  upstream-raised tailings dams has been prohibited in Brazil. In 2022, a waste slide from a sterile pile at the Pau Branco Mine in Nova Lima promoted a dike overflow. There was the death of five people whose car was buried by a landslide on a hillside. New strategies and technologies, such as reprocessing and recycling, can be tested to ascertain whether they can help improve practices in tailings management. Indeed, mining companies' corporate responsibility and sustainability practices need to be evaluated to verify whether they better match expectations. On the other hand, more specific and detailed regulations and resolutions are required to ensure the safe monitoring and management of sterile waste piles. This paper presents a review of the facts, a discussion of the literature (mainly on recent tailings dam disasters), the current situation of mining-containing waste structures in Brazil, a brief sustainability analysis and perspectives aimed at preventing/minimising catastrophes in the future.

Multispecies and multibiomarker assessment of fish health from Iguaçu River reservoir, Southern Brazil

This study investigated the impact of micropollutants on fish health from Segredo hydroelectric reservoir (HRS) along the Iguaçu River, Southern Brazil, contaminated by urban, industrial, and agricultural activities. This is the first comprehensive study assessment in the river after the severe drought in the 2020s in three fish species from different trophic levels Astyanax spp. (water column depth/omnivorous), Hypostomus commersoni (demersal/herbivorous), and Pimelodus maculatus (demersal/omnivorous). Animals, water, and sediment samples were collected from three distinct sites within the reservoir: Floresta (upstream), Iratim (middle), and Station (downstream). The chemical analysis revealed elevated concentrations of metals (Al, Cu, Fe) and the metalloid As in water, or Cu, Zn, and As in sediment, surpassing Brazilian regulatory limits, while the organic pollutants as DDT, PAHs, PCBs, and PBDEs were found under the Brazilian regulatory limits. The metal bioaccumulation was higher in gills with no significant differences among sites. The species Astyanax spp. and H. commersoni displayed variations in hepatosomatic index (HSI) and P. maculatus in the condition factor index (K) between sites, while adverse effects due to micropollutants bioaccumulation were observed by biochemical, genotoxic, and histopathological biomarkers. The principal component analysis and integrated biomarker response highlighted the upstream site Floresta as particularly inhospitable for biota, with distinctions based on trophic level. Consequently, this multifaceted approach, encompassing both fish biomarkers and chemical analyses, furnishes valuable insights into the potential toxic repercussions of micropollutant exposure. These findings offer crucial data for guiding management and conservation endeavors in the Iguaçu River.

Physiological strategies of acute thermal conditions of Rhamdia voulezi collected in the Iguaçu river watershed, Paraná, Brazil: biochemical markers of metabolic and oxidative stress

Thermal pollution creates substantial challenges that alter energy demand and produce reactive oxygen species that damage fish DNA, proteins, and lipids. Rhamdia voulezi is a species of fish native to the Iguaçu river, Paraná, Brazil, that does not have scientific records of minimum (CTmin) and maximum (CTmax) temperatures required for survival. As it is a top predator species in the food chain and lives at temperatures below 22 °C, the loss of the species can cause functional problems in controlling the ecosystem and energy flow. The study evaluated the tissue metabolism of the brain, heart, and muscle of R. voulezi (n = 72) subjected to acute thermal stress of 31 °C for 2, 6, 12, 24, and 96 h after acclimatization to 21 °C. The biochemical markers SOD, GPx, MDH, HK, and CK of the brain, PCO of the heart and CAT, glycogen, G6PDH, and ALT of muscle were significant. PCA, IBR, thermal sensitive, and condition factor suggested that R. voulezi has different physiological strategies for acclimatization to 31 °C to mobilize and sustain the metabolic needs of oxygenation and energy allocation/utilization for tissue ATP production.

Spatial-temporal variations of metals and arsenic in sediments from the Doce River after the Fundão Dam rupture and their bioaccumulation in Corbicula fluminea

The rupture of the Fundão dam in Brazil released tons of mining tailings into the Doce River Basin (DRB). This investigation aimed to determine the bioaccumulation of metals in soft tissues of the bivalve Corbicula fluminea exposed to sediments collected in the DRB in four periods (just after, 1, 3, and 3.5 years after the dam rupture). In the exposure bioassays, the concentrations of Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in sediments and bivalve soft tissues were quantified. The concentration of some elements (As, Cd, Mn, and Al) in sediments exceeded the federal limits or regional backgrounds at some sampling sites, but their concentrations tended to decrease over time. However, higher concentrations of many elements were detected in the winter of 2019. Several elements were detected in C. fluminea soft tissues, but the bioaccumulation factors were generally low or not related to those elements associated with the ore tailings, evidencing that the bioavailability of metals to bivalves, in laboratory conditions, was limited. Integr Environ Assess Manag 2024;20:87-98. © 2023 SETAC.

A large scale temporal and spatial environmental DNA biodiversity survey of marine vertebrates in Brazil following the Fundão tailings dam failure

Seawater contains a wealth of genetic information, representing the biodiversity of numerous species residing within a particular marine habitat. Environmental DNA (eDNA) metabarcoding offers a cost effective, non-destructive method for large scale monitoring of environments, as diverse taxonomic groups are detected using metabarcoding assays. A large-scale eDNA monitoring program of marine vertebrates was conducted across three sampling seasons (Spring 2018, Autumn 2019; Spring 2019) in coastal waters of Brazil. The program was designed to investigate eDNA as a testing method for long term monitoring of marine vertebrates following the Fundão tailings dam failure in November 2015. While no baseline samples were available prior to the dam failure there is still value in profiling the taxa that use the impacted area and the trajectory of recovery. A total of 40 sites were sampled around the mouths of eight river systems, covering approximately 500 km of coastline. Metabarcoding assays targeting the mitochondrial genes 16S rRNA and COI were used to detect fish, marine mammals and elasmobranchs. We detected temporal differences between seasons and spatial differences between rivers/estuaries sampled. Overall, the largest eDNA survey in Brazil to date revealed 69 families from Class Actinopterygii (fish), 15 species from Class Chondrichthyes (sharks and rays), 4 species of marine and estuarine mammals and 23 species of conservation significance including 2 species of endangered dolphin. Our large-scale study reinforces the value eDNA metabarcoding can bring when monitoring the biodiversity of coastal environments and demonstrates the importance of collection of time-stamped environmental samples to better understand the impacts of anthropogenic activities.

Doce river mining tailings can be an influencing factor in loggerhead turtles reproductive success in Brazil

In November 2015, a tailings dam ruptured and affected the second largest nesting site of loggerhead sea turtles in Brazil. This study aimed to evaluate the reproductive success, and trace elements in female's plasma, freshly laid eggs, unhatched eggs, and dead hatchlings of loggerhead turtles that nest in the coastal area exposed to the mining waste (Povoação, Espírito Santo state) and compare them with animals from an area that was not affected by the tailings (Praia do Forte, Bahia state). Plasma concentrations of As, Cd, Cr, Fe, and Zn were significantly higher in samples from Povoação in comparison to turtles from Praia do Forte. In Povoação, unhatched eggs and dead hatchlings had higher As, Cu, Hg, Mn, and Zn concentrations than freshly laid eggs, and trace elements correlated with the hatching and emergence success. Our findings suggest that the higher concentrations of some metals may influence the incubation period and reproductive success of loggerheads in the affected area.

Impacts of mining pollution on coastal ecosystems: is fish body condition a reliable indicator?

Identifying reliable biological indicators is fundamental to efficiently assess human impacts on biodiversity and to monitor the outcomes of management actions. This study investigates whether body condition is an appropriate indicator of putative effects from iron ore mining tailings on marine fishes, focusing on the world's largest mining disaster - known as the Mariana disaster, in Brazil. Eight species were used to test the hypothesis that individuals inhabiting an area severely impacted by tailings have reduced body condition in comparison to those in control areas near (<60 km) and distant (>120 km) from the impact site. Contrary to our prediction, no significant difference in condition was detected between the impacted area and both near and distant controls in seven of the eight species. The results indicate that body condition, as measured by the scaled mass index, has limited applicability as indicator of impact from mining pollution on the fishes analysed. Hypotheses that could explain our findings are proposed, including nutrient provisioning from continental drainage that could indirectly influence fish condition and compensate for the deleterious effects of mining pollution.

Fungal bioproducts for petroleum hydrocarbons and toxic metals remediation: recent advances and emerging technologies

Petroleum hydrocarbons and toxic metals are sources of environmental contamination and are harmful to all ecosystems. Fungi have metabolic and morphological plasticity that turn them into potential prototypes for technological development in biological remediation of these contaminants due to their ability to interact with a specific contaminant and/or produced metabolites. Although fungal bioinoculants producing enzymes, biosurfactants, polymers, pigments and organic acids have potential to be protagonists in mycoremediation of hydrocarbons and toxic metals, they can still be only adjuvants together with bacteria, microalgae, plants or animals in such processes. However, the sudden accelerated development of emerging technologies related to the use of potential fungal bioproducts such as bioinoculants, enzymes and biosurfactants in the remediation of these contaminants, has boosted fungal bioprocesses to achieve higher performance and possible real application. In this review, we explore scientific and technological advances in bioprocesses related to the production and/or application of these potential fungal bioproducts when used in remediation of hydrocarbons and toxic metals from an integral perspective of biotechnological process development. In turn, it sheds light to overcome existing technological limitations or enable new experimental designs in the remediation of these and other emerging contaminants.