Biochemical and physiological aspects of restinga herbaceous plants tolerance to iron ore tailing plume along the coastal region of Espírito Santo-Brazil

Abstract

In Brazil, the worst environmental disaster involving mining dams was the collapse of the Fundão tailing dam, in 2015. This accident affected directly the ecosystems of the regions surrounding the Doce River Basin. After continuous contamination of soils with heavy metals, only plants able to cope with the toxic effects of these elements can survive under this stressful environment. Thus, the main goal of this study was to carry out a detailed post-disaster analysis during two sampling periods to identify physiological and biochemical markers allowing us to understand the metabolic impact of heavy metals on Restinga herbaceous species. We determined the concentrations of heavy metals and antioxidant compounds, and further performed gas exchange analyses coupled with detailed biochemical analyses. These analyses were performed in two herbaceous species at seven Restinga stations along the coastal region of Espírito Santo - Brazil. The deposition of heavy metals such as iron and manganese varied considerably between the seven sampling stations and adaptive mechanisms to cope with excessive metals levels were verified in the herbaceous species. We observed several physiological and biochemical responses to metals that indicated potential adaptive mechanisms. Adjustments in the photosynthetic-related parameters including an acute reduction in stomatal conductance and transpiration rates associated with high stomatal resistance were noticed. Moreover, gradual reduction in pigments levels from the most distant stations to the ones closest to the Doce River mouth was noted in herbaceous species. Changes in the metabolism of nitrogen as protein content, carbon, and antioxidants were also noticed. Notably, variable responses according to the species and sample period demonstrate the further need for analysis over time to confirm the identified bioindicators.