Mercury in Fish from the Xingu River in Environments Influenced by the Belo Monte Hydroelectric Plant, Amazon, Brazil
DOI:
https://doi.org/10.5132/eec.2026.01.05Keywords:
Anthropogenic impacts;, contamination;, Potentially Toxic Elements (PTEs);, reservoirs, fishAbstract
Hydropower plants are widely recognized for their environmental impacts. These projects can lead to increased mercury (Hg) levels in Amazonian rivers by altering the functioning of these aquatic systems. Our study examined Hg concentrations in water, sediments, and tissues of two fish species in the Xingu River, sampled at eight points (P1 to P8) affected by the Belo Monte Hydroelectric Plant (Pará, Brazil). The highest sediment Hg concentrations were found within the reservoir, while the lowest concentrations were recorded downstream of the reservoir. The peacock bass (Cichla melaniae, a piscivorous species) exhibited higher tissue Hg concentrations than the Golden Nugget Pleco (Baryancistrus xanthellus, a detritivorous species). Both species showed the same tissue Hg concentration pattern: liver > muscle > gill. In C. melaniae, Hg concentrations in all three tissues increased proportionally with body size. In B. xanthellus, there was a tendency for gill Hg concentrations to decrease with increasing total length. B. xanthellus
presented higher Hg concentrations in the reservoir than in other sampling sites. In C. melaniae, gill Hg concentrations differed between P1 (upstream of the reservoir and outside the hydroelectric plant’s influence) and P3 (in the reduced flow section of the dam). The muscle tissue Hg concentrations of both species remained within the safety limits established by Brazilian legislation for human consumption. This study enabled us to evaluate Hg levels in fish, water, and sediments of the Xingu River after the construction of the Belo Monte Hydroelectric Plant and to compare them with levels observed in other areas influenced by hydropower plants.
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