Avaliação morfofisiológica do fígado de duas espécies de peixes (Oligosarcus argenteus E Hoplias intermedius) em ambientes impactados pelo rompimento da barragem do Fundão na bacia do rio Doce

Abstract

The collapse of the Fundão dam in Mariana-MG was responsible for the greatest contamination by mining waste in aquatic ecosystems in the world. Immediate impacts were observed on the fish fauna residing in the rio Doce basin, such as fish mortality, however the biota residing in areas contaminated by the tailings is chronically exposed to mining residues accumulated in the sediment and river bank. Chronic exposure of fish to heavy metals derived from waste can trigger metabolic changes that result in cellular and oxidative stress, which can generate serious pathologies in various organs of the species subjected to this exposure in the ecosystem. The objective of this study was to evaluate the morphophysiology of the liver and the possible pathological effects in two species of fish (Oligosarcus argenteus and Hoplias intermedius) collected in environments impacted by the collapse of the Fundão dam in the Rio Doce basin. A pilot sampling and four quarterly samplings were carried out over a period of one year at three points in the Doce River basin and a reference stretch on the Piranga River, not impacted by waste from the collapse of the Fundão dam. Liver, water and sediment samples were analyzed for their metal concentrations at their respective sampling points. The liver of these species was analyzed for histopathologies and expression of biomarker molecules for metals (metallothionein), xenobiotics (cytochrome P4501A), oxidative stress (catalase, glutathione peroxidase and superoxide dismutase) and cell death by apoptosis (caspase-3) and necrosis (HMGB1). Metal analysis demonstrated variations in Fe and Mn in the water, As, Fe and Mn in the sediment and variations in As, Fe and Hg in the liver of O. argentes and Cd, Fe and Hg in the liver of H. intermedius collected at the points impacted by waste. Furthermore, specimens collected from impacted points showed higher values for their respective indices of histopathological alteration. The biomarker molecules evaluated showed characteristics of response to oxidative stress and variations in their respective densitometry at points impacted by mining waste. The results of the present study demonstrate the molecular alterations and the effects of bioaccumulation and biomagnification resulting from exposure by heavy metals from the collapse of the Fundão dam.