Mangroves as traps for environmental damage to metals: The case study of the Fundão Dam

Abstract

This essay is a conceptual framework for testing the causal mechanisms of system degradation by metals in the mangrove ecosystem. The Fundão Dam collapse caused massive damage to the marine environment on the Southern Atlantic and Brazilian coast, reaching various kilometers from its origin, becoming a source of contamination. Along this Brazilian coast are vast mangrove areas with high biodiversity, different geomorphology, and distinct ecological functioning. These mangroves support fisheries' productivity in the Tropical South Atlantic, in connection with Abrolhos Reef. Brazil does not have a protocol to monitor environmental damage in this ecosystem, and we proposed to develop a way to identify the impact and quantify it. Along the estuaries, to assess the damage, the plots were demarked in three regions: the upper, middle, and lower estuary, and in both types of forest: fridge and basin. Samples of sediment and leaves were collected bi-monthly to evaluate metal concentrations, especially iron and manganese, the most abundant metals in Fundão Dam. The monitoring also evaluated the forest structure, dynamics of the crabs' population, and flora productivity. First-year monitoring identifies a high concentration of iron or manganese in the sediment above the NOAAs' recommendation in all the estuaries. The concentration of Fe and Mn in sediment varies seasonally in magnitude, concentration, and types of metals between estuaries, sectors, and forests. The behavior of biological indicators in the presence of metals (type and concentration) differed between fauna and flora species. The monitoring recognized that the tailings mining from Fundão Dam impacted all estuaries by different magnitudes and persistence. These differences are due to geomorphology diversity, climate, and oceanographic influences.