Samarco dam breach : an environmental disaster on a highly impacted river basin and the use of Leaf Fluctuating Asymmetry for bioindication.

Abstract

In November 2015, the Doce River hydrographic basin, one of the main river basins in Brazil with an European occupation varying from 200-300 years, suffered an environmental disaster, caused by the breach of a mining tailing dam (Fundão dam). We evaluated leaf Fluctuating Asymmetry (FA) as a proxy for environmental stress, along with herbivory levels and specific leaf area (SLA) from plants in a community of riparian vegetation impacted by the iron tailings resulted from this disasters along the Doce River basin. True patterns of FA were detected in the community of riparian plants from the upper Doce River basin. We did not find, however, significant differences in FA levels for the plant community in control and impacted areas, neither for levels of herbivory. However, when comparing the points in upper and mid Doce River, herbivory levels were higher in the mid basin. The same pattern was observed for the SLA levels, indicating that plants from the mid Doce River may have better nutritional quality, being more consumed by herbivores. Although plants in the areas studied are asymmetric, it appears that the mining toxic mud did not represent a source of impact capable to increase further asymmetry to the levels already found in plant communities in places where the tailings did not reach. The long history of degradation of the Doce River basin may be a source of stress in the plant community parallel to that caused by the mud. Thus, other factors associated with land-use intensity and abiotic factors may influence plant stress, levels of asymmetry and herbivory and deserve further investigation.