Fish from the Doce river basin seven years after the Fundão dam rupture: an isotopic approach

Abstract

Aquatic ecosystems are under a high level of threat due to human activities. The Doce river basin has an intense history of exploration and alteration of its environments, related to the most diverse human activities. In 2015, there was the rupture of the Fundão dam in Mariana, MG, which contaminated the bed of the Doce River with 66 million m3 of mining waste, adding to the various other impacts that affect this basin. The main objective of this thesis is to evaluate the effects of the presence of pollutants and the rupture of the dam in Mariana on the trophic structure of the ichthyofauna of the Doce river basin, through the use of stable isotopes of carbon and nitrogen. In the first chapter we focused on evaluating the trophic structure of the Santo Antônio river, a tributary in good environmental condition in the Rio Doce basin. We evaluated the isotopic stability of the fish community in this river, in order to have a basis for comparison with other points that were impacted by mining tailings. The trophic structure remained isotopically stable over the years of collection. In the second chapter, we assessed the temporal variation in species richness and trophic diversity at sites affected and unaffected by mining tailings. Unaffected regions exhibited higher species richness and greater stability in trophic metrics. The region closest to the impact showed significant temporal instability in trophic metrics, while more distant impacted regions tended to approach the trophic metrics found in control regions.