Name: Fabrício Ângelo Gabriel
Type: PhD thesis
Publication date: 16/09/2021
Advisor:
Name |
Role |
|---|---|
| Angelo Fraga Bernardino | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| Angelo Fraga Bernardino | Advisor * |
| Jean-Christophe Joyeux | Internal Alternate * |
| Matilde Maria Moreira dos Santos | External Examiner * |
| Pablo Muniz Maciel | External Examiner * |
| Rachel Ann Hauser Davis | External Alternate * |
| Ryan Carlos de Andrades | External Examiner * |
| Sergio Antonio Netto | External Examiner * |
Summary: The Rio Doce estuary was strongly impacted by the plume of tailings and sediment from the Fundão dam collapse in Minas Gerais state, Brazil. The tailings spill and its arrival in the estuary caused catastrophic ecological and socio-economic consequences. Short-term impacts revealed an immediate reduction in biodiversity and prolonged biological effects of chronic contamination by metals and metalloids. This thesis presents an assessment of the contamination and its long-term effects (2017 to 2020, two to four years after the disaster) after the plume arrival in the estuarine environment, using multiple lines of evidence to reveal potential ecological impacts and risks to the aquatic biota. The present approach includes physicochemical analyzes of sediments, determination of bioaccumulation of chemical elements in aquatic fauna, biosynthesis of oxidative stress biomarkers in fish, and effects on structure and composition of estuarine benthic assemblages. Therefore, the thesis chapters progressively reveal the contamination and the ecological and biological effects of elements associated with mine tailings in the estuarine ecosystem. The first chapter highlights the high contamination of the estuary by potentially toxic elements and the associated ecological risks, evidencing the fragility of the estuarine ecosystem in face of acute and chronic impacts caused by the mine tailings spill. The second chapter consists of a long-term analysis of the presence of metals in sediments and an integrated assessment of contaminants, revealing their seasonal variability and the persistence of possible adverse biological effects on the estuarine fauna. The third chapter makes use of proteomics and metallomics analysis to investigate the exposure of the ichthyofauna to contaminants, suggesting that many species are chronically impacted and bioaccumulate metals and metalloids. The fourth chapter focuses on the study of impacts on benthic assemblages after the initial impact (acute) of the arrival of mine tailings. For this purpose, pre-impact ecological data were combined with long-term data (4 years post-disaster). Although there is an explicit decline in the metals concentrations in estuarine sediment, there has been a stabilization of levels above the reference value for the estuary, probably reflecting a slow recovery of benthic assemblages and continued loss of biodiversity. Finally, the fifth chapter
makes an integrative and conclusive synthesis with the multiple lines of evidence used to contribute to the estuarine environmental management after the mine tailings spill in the Rio Doce, as well as to stimulate future studies. The results reported here suggest lasting effects on the ecological system, in which the estuarine biota will continue under chronic disturbance associated with the presence of tailings and metals.
