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.

在过去的几十年中，世界范围内的大型多样化河流（例如亚马逊河及其支流）经历了几次人为驱动的转变，尽管影响评估通常缺乏基线数据或参考值来更好地估计观察到的扰动。在这里，我们评估了鱼肌肉组织中的 THg 和 δ ¹⁵ N，以确定生物放大过程，还包括季节性评估，这些过程涉及来自位于新谷河的 Belo Monte 水库的鱼类在蓄水前的汞含量。共采集了来自不同饲养行会的 19 种鱼类的 312 个样本。没有人表示 THg 浓度高于世界卫生组织制定的 0.5 μg g ^{-1阈值水平。}然而，观察到生物放大（R = 0.8; p  < 0.001），整个食物网的营养放大系数 1.76 也证实了这一点。水中的 THg 含量小于 0.001 mg L ^-1并且只有Hemiodus unimaculatus呈现出 THg 的季节性变化。因此，在本研究期间，新谷河的水体和目标鱼的汞污染水平均较低。