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Brazilian soils can have high concentrations of toxic elements, mainly mercury (Hg) and arsenic (As), metals also associated with anthropogenic activities (e.g. intensive agriculture, mining, deforestation and hydroelectric plants). This can lead to large amounts of these elements reaching and/or being mobilized in the aquatic ecosystem, which constitutes a serious threat to the environment and to the health of local populations. Thus, we evaluate the feasibility of analyzing the tissues of freshwater fish species for monitoring toxic and trace element accumulation within the aquatic ecosystem in the Lower Amazon, Brazil. Two fish species were considered: Cichla temensis (Tucunaré), a carnivorous species, and Pterygoplichthys pardalis (Acari), a detritivorous species. Samples of liver and muscle from both species were evaluated in relation to their potential use for biomonitoring purposes. The study findings clearly demonstrate the value these fish species and tissues, particularly liver, for biomonitoring toxic and trace element concentrations in the aquatic environment across the study region. While Tucunaré liver proved the best option for biomonitoring elements that accumulate through the food chain (e.g. Hg), Acari liver better reflected elements that typically accumulate in the sediments (e.g. As). Moreover, the trace element profiles, determined using chemometric (multivariate) techniques, differed greatly in specimens from waters in the Andean mountain range (sampling sites located in the main course of the Amazon River) with high sediment concentrations, and in specimens from the Guyana and Brazilian shields (Porto Trombetas on the Trombetas River and Itaituba on the Tapajós River). The findings also indicate that deposition of elements in freshwater fish in this area is mainly associated with the geological origin of the soils and that large amounts of toxic elements can reach the aquatic ecosystem due to anthropogenic activities, thereby posing a serious danger to the environment and the health of the riverside communities. [Display omitted] • The Amazon region is affected by mining and dams, impacting the on aquatic ecosystems. • Tucunaré and Acari tissues were analyzed for toxic/trace elements. • Fish tissues can be used for biomonitoring toxic and trace element concentrations. • Tucunaré liver can be used to biomonitoring metals that accumulate through the food chain. • Acari liver can be used to biomonitoring elements that typically accumulate in the sediments. [ABSTRACT FROM AUTHOR]

• Metal in freshwater shrimps does not pose a significant risk for human consumption. • Amazon and Tapajos had different metal accumulation, related with mining activities. • Metal analysis could be used to distinguish the shrimp origin for commercial purposes. • Bioaccumulation of Fe, Co and Mn was mainly in shrimp viscera from Amazon river. This study aimed to evaluate the concentrations of toxic elements (As, Cd, Hg, Pb) and essential trace elements (Co, Cu, Cr, Fe, Mn, Mo, Ni, Se, Zn) in the freshwater shrimp M. amazonicum in the region of Santarem (lower Amazonia), which is affected by mining activities. The level of metal accumulation in the shrimp was found to be similar to that measured in other regions affected by anthropogenic polluted in both in Brazil and elsewhere, and does not pose a significant risk for human consumption. The different patterns of metal accumulation between the Amazon and Tapajos basins appear to be (at least partly) related to respectively bauxite exploitation and gold mining in the region. Bioaccumulation of the trace elements Co, Fe, and Mn mainly occurred in the visceral part of the shrimps from the Amazon river. [ABSTRACT FROM AUTHOR]

The Lower Amazon region (Western Pará, northern Brazil) is greatly affected by mining exploitations (particularly artisanal gold mines) and other industrial and intensive agricultural activities with potentially strong impacts on aquatic ecosystems. Although such impacts include contamination with various toxic elements, to date only the effects of Hg have been considered. In this study, toxic and trace element concentrations were determined in the flesh of 351 fish specimens, including detritivores (Acarí, Pterygoplichthys pardalis), omnivores (Piranha, Pygocentrus nattereri; Pirarucu, Arapaima sp.) and carnivores (Caparari, Pseudoplatystoma fasciatum; Tucunaré, Cichla ocellaris), during the dry and wet seasons in 2015 and 2016. The range of concentrations of toxic element residues were 2-238 μg/kg fresh weight for As, 1-77 μg/kg for Cd, 4-1922 μg/kg for Hg and 1-30 μg/kg for Pb. Only the maximum concentrations of Hg established in the Brazilian legislation for fish destined for human consumption (0.5 mg/kg) were exceeded (in 16% of carnivorous species). The large between-species and seasonal differences observed for all these toxic elements are probably related to the seasonal behaviour and dietary habits of the different fish species. By contrast, essential trace element concentrations were low and not related to seasonal or dietary factors, and the observed differences may be at least partly related to the metabolism of each species. The associations between Hg and the essential trace elements Se, Fe, Co and Mn deserve special attention, as these trace elements may play a role in Hg cycling and methylation and merit further evaluation with the aim of reducing Hg toxicity in aquatic environments., 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 © 2020 Elsevier B.V. All rights reserved.)