Fabio Cavalca Bom

Large-scale disturbances can profoundly alter aquatic ecosystems by modifying water chemistry, sediment dynamics, and biodiversity across connected freshwater and marine environments. The 2015 Fundão Dam collapse in Brazil provides an unprecedented context to evaluate how multiple aquatic communities respond to intense and prolonged contamination, revealing key mechanisms of community reorganization under chronic anthropogenic impacts. By a multi-taxa monitoring dataset collected from 62 freshwater and marine sites, we analyzed how different communities, comprising phytoplankton, zooplankton, macroinvertebrates, and fish, responded along a gradient of mining tailing exposure. Applying threshold indicator taxa analysis (TITAN), we identified critical environmental variables, capturing tipping points for positive and negative biotic responses to tailing-related environmental gradients. Our results showed that mining-related contaminants, combined with hydrogeochemical alterations triggered by the dam collapse, have driven long-term changes in biodiversity, reshaping ecosystem functioning. The same stressors that caused widespread negative responses in community structure also promoted localized increases in opportunistic, mainly planktonic taxa, indicating a multidirectional community reorganization. In general, small increases in metals and hydrogeochemical alterations (such as turbidity up to 17 NTU in riverine systems and 2 NTU in the marine sites), resulting from the dam collapse have driven persistent changes in biodiversity, ultimately reshaping ecosystem functioning. Integrating community-level thresholds should represent a critical approach to improve the detection of regime shifts and to support the development of habitat-specific recovery strategies for riverine and marine ecosystems affected by mining disturbances.

Large-scale disasters can result in chronic pollution of coastal environments with unanticipated and poorly quantified impacts, such as the reshaping of marine connectivity. A recent example is the collapse of the Fundão tailings dam in 2015, which released about 50 million m³ of mine waste into the Doce River, affecting one of Brazil’s largest estuarine–mangrove systems. Here, we combine a high-resolution CROCO hydrodynamic simulation with an individual-based Lagrangian model (Ichthyop) to track the dispersal of mangrove crab (Ucides cordatus) larvae from four estuaries along the southeastern Brazilian margin between 2022 and 2024. Trajectories crossing seasonal msPAF fields derived from in situ water-quality measurements were used to quantify larval exposure to contaminants from mine waste. These fields were based on measured concentrations of As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V, Zn, and Al. Results show that surface shelf flow and mesoscale activity in the vicinity of the Doce River mouth contribute to offshore export of larvae, while the reef-dominated Abrolhos shelf promotes retention. Interannual variability alternates between long-distance export and local retention, associated with regional climate variability. Larval mortality rates caused by offshore advection and lethal temperature are high (65–75%). In addition to these modeled mortality sources, surviving cohorts frequently crossed areas with elevated msPAF values during transport, indicating potential exposure to metal(loid) mixtures. This suggests that the regional connectivity of U. cordatus is under chronic stress that likely compromises the integrity and resilience of coastal populations, since southern estuaries depend strongly on northern larval sources. The integration of Lagrangian simulations with in situ contaminant monitoring and spatially explicit exposure metrics demonstrates that transport pathways regulate not only connectivity among estuaries but also the duration and intensity of larval exposure to pollutants.

The Fundão tailings dam marks its 10th year of disaster in 2025, underscoring the need for a critical assessment of the studies related to the impacts on aquatic ecosystems caused by the largest disaster in mining history. In this context, the present study aimed to review articles that, throughout the years, have investigated changes in the Doce River basin, as well as in coastal and marine areas affected by this collapse. We applied a systematic analysis of the published literature, identifying the main results in relation to the methodologies applied. Therefore, the studies were characterized according to their methodological approaches, spatiotemporal efforts, environmental compartments, and topics of study evaluated. In total, 182 articles published between 2016 and July 2025 were considered. Considerable heterogeneity was observed regarding spatial and temporal coverage, ranging from point‐in‐time assessments to large-scale analyses. Most of the reviewed studies revealed both acute and chronic effects on water and sediment quality across all monitored environments, which in turn resulted in significant impacts on biodiversity. Some studies investigated all environments in an integrated manner, which made possible a deeper understanding of the connections between these systems, showing the importance of this type of approach. Together, the studies revealed the challenge of learning from disasters, especially regarding environmental issues. Furthermore, they encouraged a critical perspective for long-term monitoring planning and the next steps needed to address aquatic biota recovery. This synthesis underscores the critical need for long-term, integrated monitoring to effectively guide the recovery of these interconnected ecosystems.

Large-scale disasters can result in chronic pollution of coastal environments with unanticipated and poorly quantified impacts, such as the reshaping of marine connectivity. A recent example is the collapse of the Fundão tailings dam in 2015 that released about 50 million m3 of mine waste into the Doce River, affecting one of Brazil’s largest estuarine–mangrove systems. Here, we combine a high-resolution CROCO hydrodynamic simulation with an individual-based Lagrangian model (Ichthyop) to track the dispersal of mangrove crab (Ucides cordatus) larvae from four estuaries along the southeastern Brazilian margin between 2022 and 2024. Trajectories crossing toxicity fields derived from in situ collections (msPAF, based on species sensitivity distributions) were used to quantify larval exposure to contaminants from mine waste. Results show that surface shelf flow and mesoscale activity in the vicinity of the Doce river mouth contribute to offshore export of larvae, while the reef-dominated Abrolhos shelf promotes retention. Interannual variability alternates between long-distance export and local retention, likely reflecting climate-driven anomalies such as ENSO. Larval mortality rates caused by offshore advection and lethal temperature are high (65–75%), with surviving cohorts frequently crossing high-contamination zones. This suggests that the regional connectivity of U. cordatus is under chronic stress that likely compromises the integrity and resilience of coastal populations, since southern estuaries depend strongly on northern larval sources. The integration of Lagrangian simulations with in-situ contaminant monitoring and spatially explicit exposure metrics demonstrate that transport pathways regulate not only connectivity among estuaries but also the duration and intensity of larval exposure to pollutants.

We present a novel approach to structure and interpret long-term environmental monitoring data, by combining the Adverse Outcome Pathway (AOP) concept with probabilistic causal modeling. To that end, a large-scale monitoring program which assessed the impacts of the collapse of a large tailings dam in southeastern Brazil in 2015 was used as our case study. Six years of monitoring (2018–2024) across the river towards the sea provided data to integrate under our framework, including dissolved metal(loid)s, fish bioaccumulation, and sub-individual biomarkers. First, metal(loid)s quantified in the water column was integrated into an index, which characterized the environmental gradient by translating the toxic pressure from the river to the sea. Then, within the AOP framework, biomarkers of antioxidant defense, oxidative damage, and tissue injury were mapped to a growth-related outcome and integrated using piecewise structural equation mixed-effects modeling. Toxic pressure varied across the environmental gradient, being consistently higher in the river, decreasing towards the sea. Biomarker responses reflected these area-specific pressures: in the river, metallothionein, lipid peroxidation, and histopathological lesions were strongly associated with toxic pressure and specific metals, whereas in marine environments, responses were weaker and largely influenced by species or temporal variability. Notably, lesions were consistently linked to oxidative stress and, in the freshwater, negatively associated with fish condition index, suggesting that tissue-level damage can scale up to growth impairment. Overall, biomarker responses revealed both expected and unexpected patterns, highlighting the context-dependent nature of defense mechanisms under mixed-metal exposure and the value of integrated approaches to environmental monitoring.

The ingestion of microplastics (particles smaller than 5 mm) by bivalves in the environment is already well established, but more laboratory studies are still needed to enable the assessment of the impacts of these particles in these organisms. In this sense, this study aimed to verify the ingestion of microplastics by bivalves in different experimental environments. For this, 60 specimens of the mussel Perna perna (Linnaeus, 1758) were exposed to different concentrations (25, 50, and 100 MPs.L^-1), sizes (1 to 2; 2.5 to 3.5; and ≥ 5 mm), and thicknesses (thick: 0.2 mm, polyethylene; and thin: 0.03 mm, polyester) during 24 h. The results showed that organisms prefer thin particles, and it was found that only one thick fiber was retained, while 23 thin particles were ingested. On the other hand, no significant differences in the uptake of fibers at different concentrations and sizes were identified, showing low concentrations of particles regardless of the treatment. We concluded, via this study, that mussels can ingest fibers of different sizes, thicknesses, and concentrations in the experimental environment, even over a short period of time (24 h). Moreover, it was observed that thickness probably was the main factor for fiber ingestion by mussels, with the thinner particles being preferentially ingested. Therefore, we suggest that new physiological studies employ fiber thickness as a preponderant factor for the ingestion of microplastics in bivalves and also that they choose sizes and concentrations similar to those found in the environment, enabling more robust and accurate results.