The rupture of the Fundão dam stands as one of the most significant environmental disasters of its kind on a global scale, profoundly affecting the aquatic ecosystem of Doce River Basin. By employing stable isotopes of carbon and nitrogen, we were able to trace matter and energy flow within ecosystems. In this study, we assessed the spatial and temporal variation, between 2020 and 2022, in species richness and trophic diversity in areas exposed (along a gradient in the main channel of the river) or unexposed (control sites in tributaries systems) to the mine ore tailings in the Doce River Basin. We tested the hypothesis that tailings reduce species richness, and that trophic stability is negatively affected by mining tailings. To estimate trophic stability for each sampling site, we calculated the standard ellipse area (SEA) and six community-wide metrics based on stable isotopes. The three regions studied presented distinct patterns on trophic diversity. Control sites exhibited stability in trophic metrics over time. Affected regions close to the rupture of the dam exhibited significant fluctuations on all six community-wide metrics analyzed than the affected regions farther from the rupture. Sites close to the rupture exhibited lower species richness, affecting mainly herbivores and piscivores. Our findings show the potential of using the isotopic approach in monitoring the ecological recovery of impacted ecosystems.