Elizete Rizzo

Metal pollution in aquatic environments represents a recurring global concern; however, traditional paradigms often assume linear bioaccumulation patterns that may fail under catastrophic contamination scenarios. This study evaluated metal concentrations in water, sediment, and tissues of 10 fish species from different trophic guilds in the Paraopeba River after the Brumadinho dam collapse. Multivariate analyses (principal component analysis [PCA], generalized linear model [GLM], and PERMANOVA) were used to explore associations between metal concentrations, ecological traits, and body size integrated with liver histopathology (Histopathological Alteration Index) and Human Health Risk Assessment. Results revealed that metal concentrations in water and fish tissues exceeded regulatory limits, whereas sediment acted as the main reservoir of metals, exhibiting higher concentrations than water. High‐severity liver damage was concentrated in benthic piscivores and benthopelagic detritivores, exposing a complex interplay between biomagnification and direct substrate contact. Human Health Risk Assessments indicated unacceptable noncarcinogenic risks driven by aluminum (Al), along with elevated carcinogenic risks for chromium (Cr) and cadmium (Cd) for both adults and children in the region analyzed. These findings demonstrate that ecological traits were associated with differences in metal accumulation, liver damage, and public health threats, reinforcing the need for nonlinear models in postdisaster regulatory frameworks.

Estrone (E1) is one of the major natural estrogens influencing the reproductive system of vertebrates. However, it contaminates aquatic environments due to runoff from livestock waste and the discharge of domestic sewage. The aim of this study was to investigate the impact of exposure to environmentally relevant concentrations of E1 on oogenesis and spawning in zebrafish ( Danio rerio ). Fish were exposed, in duplicate, to 20, 200, and 2000 ng/L of E1 for 49 days for oogenesis analysis evaluating histology, sex steroids, morphometry, cell proliferation, apoptosis, immunohistochemistry for insulin-like growth factor (IGF) and inducible nitric oxide synthetase (iNOS). 17β-estradiol (E2) and 11-ketotestosterone (11-KT) were assessed by ELISA assay. Nitric oxide production was evaluated indirectly by quantifying nitrite. Results revealed that E1 exposure altered the proportions of ovarian follicles and somatic components, with significant increase of oogonia, follicular atresia and inflammatory infiltrate, and decrease of follicular cells. Levels of E2, and immunoreaction for IGF1 increased in E120 and 200 ng/L groups, but 11-KT, IGF2 and IGF1R were not altered. Nitrite concentrations in ovaries were significantly elevated in E1 200 and 2000 ng/L groups, but iNOS immunoreaction was not altered. These changes led to reduced egg production in all groups exposed to E1 and significatively decreased fertilization rates at 200 and 2000 ng/L. Overall, the findings demonstrate that E1, even at concentrations commonly found in surface waters, has detrimental effects on ovarian development, gametogenesis and reproductive success in zebrafish. Monitoring environmental estrogens levels in aquatic environments is therefore essential for fish conservation.

Heavy metals, originating from human activities and natural processes, are a threat to aquatic organisms and the environment. As the main organ responsible for detoxification, the liver plays a fundamental role in regulating potentially harmful chemicals such as heavy metals, and the interaction between heat shock protein 70 and metallothionein may be important in processes related to cellular protection, since both participate in responses to oxidative stress and redox balance. To analyze the effects of heavy metals on the morphology and biomarkers expression in the liver of Hoplias intermedius , specimens from the Paraopeba River—contaminated environment and Abaete River—control environment were collected, and fragments of liver were sampled for histopathological and immunohistochemical analyses. Additionally, the levels of Al, Cd, Pb, Cu, Cr, Fe, Mn, and Zn were measured in water and liver from all individuals. The results showed concentrations above the permitted levels of Al, Cd, and Mn in the water, and Cd, Pb, Cr, and Fe in liver samples of Paraopeba River. Furthermore, dilatation and congestion of sinusoidal capillaries and lobular veins were observed; vacuolization of hepatocytes; formation of melanomacrophage centers; and signs of tissue necrosis were detected. In immunohistochemical analysis, metallothionein and heat shock proteins (HSP70) markings increased when compared to fish from the control environment. These results indicate the severity of the toxic effects of chronic exposure to heavy metals on aquatic biota, and a possible human health threat due to the consumption of contaminated fish.