Before the Dam: A Fish-Mercury Contamination Baseline Survey at the Xingu River, Amazon Basin Before the Belo Monte Dam.

In the last decades, mega-diverse rivers worldwide (e.g., the Amazon and their tributaries) have experienced several human-driven transformations, although impact assessments oftentimes lack baseline data or reference values to better estimate observed disturbances. Herein, we assessed THg and δ15N in fish muscle tissue to determine biomagnification processes, also including seasonal assessments, concerning Hg in fish from the Belo Monte reservoir, located on the Xingu River, prior to its impoundment. A total of 312 samples from 19 fish species belonging to distinct feeding guilds were sampled. None presented THg concentrations above the threshold levels of 0.5 µg g-1 established by the World Health Organization. However, biomagnification was observed (R = 0.8; p < 0.001), also confirmed by a trophic magnification factor of 1.76 for the entire food web. The THg content in the water was less than 0.001 mg L-1 and only Hemiodus unimaculatus presented seasonal variations for THg. Therefore, at the time of this study, the Xingu River presented low Hg contamination levels in both water and target fish.

The consumption of shark meat in the Amazon region and its implications for human health and the marine ecosystem.

Here, we evaluated the levels of As, Hg, Pb, and Cd in shark meat sold along the Amazon Coast of Brazil and used nitrogen stable isotope values to determine trophic position and to assess element biomagnification. From market samples, a total of 13 species were identified via molecular analysis, including those listed as endangered and vulnerable by the IUCN Red List. Arsenic was present in significantly higher concentrations than all other elements, followed by Hg, with the highest mean concentrations recorded in M. higmani (As: 19.46 ± 8.79 µg/g ww) and C. acronotus (Hg: 1.12 ± 0.68 µg/g ww). Lead and Cd were recorded at much lower levels in all species. The EWI of individual elements were above PTWI for all species when considering Hg, seven species for inorganic arsenic (iAs), and one species for Pb. The weekly consumption of 10 species should be reduced to less than 416.39 g, which is equivalent to the daily estimated fish consumption rate in the region. The mean (±SD) δ15N values of species ranged from 10.7 ± 0.51‰ in M. higmani to 14.2 ± 0.59‰ in C. porosus, indicating feeding over >1 trophic level. Arsenic was negatively correlated with δ15N values, while Hg was positively correlated indicating biodilution and biomagnification, respectively. Our results indicate that the sale and consumption of shark meat will expose consumers to potentially harmful levels of iAs and Hg, as well as contributing to the population decline of species including those that are currently categorized as threatened.

Mercury and methyl mercury in fishes from Bacajá River (Brazilian Amazon): evidence for bioaccumulation and biomagnification.

This study assessed total mercury (THg) and methyl mercury (MeHg) concentrations, bioaccumulation and biomagnification of THg through the food web in fishes consumed by indigenous communities of Bacajá River, the largest tributary of the right bank of Xingu River. In total, 496 fish (22 species) were sampled. Nine species had THg concentrations above the limit recommended by the World Health Organisation (0·5 µg g(-1) wet mass), and one exceeded the recommended level for Hg in predatory fishes by Brazilian law (1·0 µg g(-1) ). The average concentration of THg increased significantly with trophic guild (herbivorous to piscivorous) and trophic level, with higher accumulation in fishes with greater total length. Ninety-six per cent of all mercury was methylated. These results suggest that feeding habits determine THg concentrations in fishes and that Hg elimination rate is slow during growth, which allows greater accumulation. These findings show that fishes in the Bacajá River contain high concentrations of THg and MeHg.

Mercury concentration in different tissues of Podocnemis unifilis (Troschel, 1848) (Podocnemididae: Testudines) from the lower Xingu River - Amazonian, Brazil.

Studies using chelonians as biosentinels of environment quality or health risks associated with turtle consumption are very rare, especially in the Amazon basin. This study aims to measure Mercury levels (Hg) in muscle, liver, fat and blood of Podocnemis unifilis from the lower Xingu River, assessing the possible difference in concentration between sexes and also evaluating the potential bioaccumulation along different body sizes. Samples were collected during the dry season (October 2012) and Mercury (Hg) concentrations were analysed by Cold Vapor Atomic Absorption Spectrometry (CVAAS). A total of 29 specimens of P. unifilis of different sizes showed low levels lower than 0.2 mg/Kg). Higher Hg concentrations were found in the liver, and significant correlations between Hg concentrations in the different tissues were also detected. There was no difference between males and females and a negative correlation was found between Hg concentration and body size.

Mercury concentration in different tissues of Podocnemis unifilis (Troschel, 1848) (Podocnemididae: Testudines) from the lower Xingu River – Amazonian, Brazil / Concentrações de mercúrio em diferentes tecidos de Podocnemis unifilis (Podocnemididae: Testudines) do baixo Rio Xingu – Amazônia, Brasil

Abstract Studies using chelonians as biosentinels of environment quality or health risks associated with turtle consumption are very rare, especially in the Amazon basin. This study aims to measure Mercury levels (Hg) in muscle, liver, fat and blood of Podocnemis unifilis from the lower Xingu River, assessing the possible difference in concentration between sexes and also evaluating the potential bioaccumulation along different body sizes. Samples were collected during the dry season (October 2012) and Mercury (Hg) concentrations were analysed by Cold Vapor Atomic Absorption Spectrometry (CVAAS). A total of 29 specimens of P. unifilis of different sizes showed low levels lower than 0.2 mg/Kg). Higher Hg concentrations were found in the liver, and significant correlations between Hg concentrations in the different tissues were also detected. There was no difference between males and females and a negative correlation was found between Hg concentration and body size.

Resumo Estudos utilizando quelônios como biosentinelas de qualidade ambiental ou de riscos à saúde associados ao consumo de tartarugas são raros, especialmente na bacia amazônica. Neste estudo foram medidos os níveis de mercúrio no músculo, fígado, gordura e sangue de Podocnemis unifilis do baixo Rio Xingu. Foram avaliadas as possíveis diferenças de concentração entre os sexos e também o potencial de bioacumulação ao longo de diferentes tamanhos corporais. A etapa de amostragem ocorreu durante o período seco (Outubro de 2012) e a quantificação de Mercúrio (Hg) foi realizada através de digestão ácida e análises por Espectrometria de Absorção Atômica com Vapor Frio (CVAAS). Um total de 29 amostras de Podocnemis unifilis, mesmo em diferentes tamanhos, mostraram concentrações de Hg menores que 0,2 mg/kg. As concentrações mais elevadas de Hg foram encontradas no fígado, e também foram detectadas correlações significativas entre as concentrações de Hg nos tecidos. Não foram observadas diferenças significativas entre machos e fêmeas, sendo registrada correlação negativa entre a concentração de Hg e o tamanho do corpo.

Mercury concentration in different tissues of Podocnemis unifilis (Troschel, 1848) (Podocnemididae: Testudines) from the lower Xingu River Amazonian, Brazil

Abstract Studies using chelonians as biosentinels of environment quality or health risks associated with turtle consumption are very rare, especially in the Amazon basin. This study aims to measure Mercury levels (Hg) in muscle, liver, fat and blood of Podocnemis unifilis from the lower Xingu River, assessing the possible difference in concentration between sexes and also evaluating the potential bioaccumulation along different body sizes. Samples were collected during the dry season (October 2012) and Mercury (Hg) concentrations were analysed by Cold Vapor Atomic Absorption Spectrometry (CVAAS). A total of 29 specimens of P. unifilis of different sizes showed low levels lower than 0.2 mg/Kg). Higher Hg concentrations were found in the liver, and significant correlations between Hg concentrations in the different tissues were also detected. There was no difference between males and females and a negative correlation was found between Hg concentration and body size.

Resumo Estudos utilizando quelônios como biosentinelas de qualidade ambiental ou de riscos à saúde associados ao consumo de tartarugas são raros, especialmente na bacia amazônica. Neste estudo foram medidos os níveis de mercúrio no músculo, fígado, gordura e sangue de Podocnemis unifilis do baixo Rio Xingu. Foram avaliadas as possíveis diferenças de concentração entre os sexos e também o potencial de bioacumulação ao longo de diferentes tamanhos corporais. A etapa de amostragem ocorreu durante o período seco (Outubro de 2012) e a quantificação de Mercúrio (Hg) foi realizada através de digestão ácida e análises por Espectrometria de Absorção Atômica com Vapor Frio (CVAAS). Um total de 29 amostras de Podocnemis unifilis, mesmo em diferentes tamanhos, mostraram concentrações de Hg menores que 0,2 mg/kg. As concentrações mais elevadas de Hg foram encontradas no fígado, e também foram detectadas correlações significativas entre as concentrações de Hg nos tecidos. Não foram observadas diferenças significativas entre machos e fêmeas, sendo registrada correlação negativa entre a concentração de Hg e o tamanho do corpo.

Mercury concentration in different tissues of Podocnemis unifilis (Troschel, 1848) (Podocnemididae: Testudines) from the lower Xingu River – Amazonian, Brazil / Concentrações de mercúrio em diferentes tecidos de Podocnemis unifilis (Podocnemididae: Testudines) do baixo Rio Xingu – Amazônia, Brasil

Studies using chelonians as biosentinels of environment quality or health risks associated with turtle consumption are very rare, especially in the Amazon basin. This study aims to measure Mercury levels (Hg) in muscle, liver, fat and blood of Podocnemis unifilis from the lower Xingu River, assessing the possible difference in concentration between sexes and also evaluating the potential bioaccumulation along different body sizes. Samples were collected during the dry season (October 2012) and Mercury (Hg) concentrations were analysed by Cold Vapor Atomic Absorption Spectrometry (CVAAS). A total of 29 specimens of P. unifilis of different sizes showed low levels lower than 0.2 mg/Kg). Higher Hg concentrations were found in the liver, and significant correlations between Hg concentrations in the different tissues were also detected. There was no difference between males and females and a negative correlation was found between Hg concentration and body size.

Estudos utilizando quelônios como biosentinelas de qualidade ambiental ou de riscos à saúde associados ao consumo de tartarugas são raros, especialmente na bacia amazônica. Neste estudo foram medidos os níveis de mercúrio no músculo, fígado, gordura e sangue de Podocnemis unifilis do baixo Rio Xingu. Foram avaliadas as possíveis diferenças de concentração entre os sexos e também o potencial de bioacumulação ao longo de diferentes tamanhos corporais. A etapa de amostragem ocorreu durante o período seco (Outubro de 2012) e a quantificação de Mercúrio (Hg) foi realizada através de digestão ácida e análises por Espectrometria de Absorção Atômica com Vapor Frio (CVAAS). Um total de 29 amostras de Podocnemis unifilis, mesmo em diferentes tamanhos, mostraram concentrações de Hg menores que 0,2 mg/kg. As concentrações mais elevadas de Hg foram encontradas no fígado, e também foram detectadas correlações significativas entre as concentrações de Hg nos tecidos. Não foram observadas diferenças significativas entre machos e fêmeas, sendo registrada correlação negativa entre a concentração de Hg e o tamanho do corpo.