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This study investigated the impact of micropollutants on fish health from Segredo hydroelectric reservoir (HRS) along the Iguaçu River, Southern Brazil, contaminated by urban, industrial, and agricultural activities. This is the first comprehensive study assessment in the river after the severe drought in the 2020s in three fish species from different trophic levels Astyanax spp. (water column depth/omnivorous), Hypostomus commersoni (demersal/herbivorous), and Pimelodus maculatus (demersal/omnivorous). Animals, water, and sediment samples were collected from three distinct sites within the reservoir: Floresta (upstream), Iratim (middle), and Station (downstream). The chemical analysis revealed elevated concentrations of metals (Al, Cu, Fe) and the metalloid As in water, or Cu, Zn, and As in sediment, surpassing Brazilian regulatory limits, while the organic pollutants as DDT, PAHs, PCBs, and PBDEs were found under the Brazilian regulatory limits. The metal bioaccumulation was higher in gills with no significant differences among sites. The species Astyanax spp. and H. commersoni displayed variations in hepatosomatic index (HSI) and P. maculatus in the condition factor index (K) between sites, while adverse effects due to micropollutants bioaccumulation were observed by biochemical, genotoxic, and histopathological biomarkers. The principal component analysis and integrated biomarker response highlighted the upstream site Floresta as particularly inhospitable for biota, with distinctions based on trophic level. Consequently, this multifaceted approach, encompassing both fish biomarkers and chemical analyses, furnishes valuable insights into the potential toxic repercussions of micropollutant exposure. These findings offer crucial data for guiding management and conservation endeavors in the Iguaçu River., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Bioaccumulation studies in fish mark the initial phase of assessing the risk of chemical exposure to biota and human populations. The Iguaçu River boasting a diverse endemic ichthyofauna, is grappling with the repercussions of human activities. This study delved into the bioaccumulation of micropollutants, the early-warning effects on Rhamdia quelen and Oreochomis niloticus in the Segredo Reservoir (HRS) and the potential risk of human exposure. Two groups of caged fish in three sites of the reservoir were exposed during the autumn-winter and spring-summer, while a third group (O. niloticus) underwent a twelve-month exposure, and inorganic and organic chemicals analysis in water, sediment, and biota. Additionally, metallothionein expression and genotoxicity were employed as biomarkers. PAHs, PCBs, Al, Cu, Fe, and As in water and DDTs, Cu, Zn, and As in sediment surpassed the thresholds set by Brazilian regulations, where DDT exhibited bioaccumulation in muscle, alongside metals in liver, kidney, gills, and muscle tissues. R. quelen showed metallothionein expression whereas DNA damage and NMA frequencies were elevated in target organs and in brain and erythrocytes of O. niloticus during summer. In this species the DNA damage in liver was remarkable after twelve months. Target Hazard Quotients and Cancer Risk values shedding light on the vulnerability of both children and adults. The reservoir's conditions led to heightened sensitivity to micropollutants for R. quelen species. The data presented herein provides decision-makers with pertinent insights to facilitate effective management and conservation initiatives within the Iguaçu Basin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The Iguaçu River basin presents high ecological importance due to its expressive endemic ichthyofauna rate, but chemical pollution may threat this biodiversity. Jordão River is one of the main tributaries of Iguaçu River and contribute to this pollution status, since it drains large agricultural areas receiving domestic and industrial effluents before flowing into the Iguaçu River. The objective of the current study was to evaluate the toxic effects of the Iguaçu, Jordão, and the combination of their waters to the embryo-larval phase of R. quelen, investigating the consequences to the population by means of mathematical modelling. R. quelen fertilized eggs were exposed for 96 h to water samples from Iguaçu River upstream (IR), Jordão River (JR), and downstream of both rivers (MR). The analysis of micropollutants in the water showed that JR presented the most complex mixture of substances and elements, followed by IR, while MR showed the lower number of micropollutants detected. Survival rate was not a sensitive endpoint, while the deformity indices were higher in individuals exposed to water from the three studied sites. Superoxide dismutase activity was increased in MR, while non-protein thiol levels were reduced in MR and JR showing the antioxidant mechanism activation. The mathematical modelling revealed that fish exposed to JR would lead to the greater population reduction (46.19%), followed by IR (40.48%) and MR (33.33%). Although the results showed toxicity in all studied sites, the JR site is the most impacted by micropollutants but decrease its toxicity after dilution with Iguaçu River., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The investigation of antibodies raised against different severe acute respiratory syndrome coronavirus (SARS-CoV-2) antigens can help to determine the extent of previous SARS-CoV-2 infections in the population and track the humoral response to vaccination. Therefore, serological surveys can provide key information to better manage the pandemic and/or to implement the most effective vaccination program. Here we describe a time series anti-nucleocapsid, anti-spike IgG serological survey analysis in the city of Matinhos, PR, Brazil during the year of 2021. Seroconversion rates to the nucleocapsid antigen were not influenced by gender or age. The serological data support that the coronavirus disease 2019 (COVID-19) infection rate is ~50% higher than official numbers. Furthermore, by applying serological data, the corrected infection fatality rate was estimated to be lower than 2.4% in contrast with the official estimative of 3.6%. The rates of IgG reactive to spike antigen resembled the curve of the fraction the population that had taken the second vaccine dose. Up to 82% of spike seroconversion was detected in the end of 2021, confirming the effectiveness of the COVID-19 vaccination program in the city. This SARS-CoV-2 serological study unraveled the SARS-CoV-2 infection rates and the response to vaccination in the city of Matinhos. IMPORTANCE The investigation of antibodies raised against SARS-CoV-2 can help to determine the extent of previous SARS-CoV-2 infections and track the humoral response to vaccination. Here we describe a time series anti-nucleocapsid, anti-spike IgG serological survey in the city of Matinhos, PR, Brazil during the year of 2021. The data depicted the progression of SARS-CoV-2 infections in the city allowing the correction of the number of citizens who experienced COVID-19 and the disease fatality rate. The seroconversion rates to the spike antigen resembled the curve of the fraction of the population that had taken the second vaccine dose, thereby confirming the effectiveness of the COVID-19 vaccination program in the city.