In the Amazon and Orinoco basins, mercury has been released from artisanal and industrial gold mining since the Colonial time, as well as a result of deforestation and burning of primary forest, that release natural deposits of methyl mercury, affecting the local aquatic vertebrate fauna. This study reports the presence of mercury in river dolphins’ genera Inia and Sotalia. Mercury concentrations were analysed in muscle tissue samples collected from 46 individuals at the Arauca and Orinoco Rivers (Colombia), the Amazon River (Colombia), a tributary of the Itenez River (Bolivia) and from the Tapajos River (Brazil). Ranges of total mercury (Hg) concentration in muscle tissue of the four different taxa sampled were: I. geoffrensis humboldtiana 0.003–3.99 mg kg⁻¹ ww (n = 21, M_e = 0.4), I. g. geoffrensis 0.1–2.6 mg kg⁻¹ ww (n = 15, M_e = 0.55), I. boliviensis 0.03–0.4 mg kg⁻¹ ww (n = 8, M_e = 0.1) and S. fluviatilis 0.1–0.87 mg kg⁻¹ ww (n = 2, M_e = 0.5). The highest Hg concentration in our study was obtained at the Orinoco basin, recorded from a juvenile male of I. g. humboldtiana (3.99 mg kg⁻¹ ww). At the Amazon basin, higher concentrations of mercury were recorded in the Tapajos River (Brazil) from an adult male of I. g. geoffrensis (2.6 mg kg⁻¹ ww) and the Amazon River from an adult female of S. fluviatilis (0.87 mg kg⁻¹ ww). Our data support the presence of total Hg in river dolphins distributed across the evaluated basins, evidencing the role of these cetaceans as sentinel species and bioindicators of the presence of this heavy metal in natural aquatic environments.

中文翻译：

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亚马逊河和奥里诺科河流域海豚种群中的汞。

在亚马孙和奥里诺科盆地，自殖民时期以来，由于手工和工业金矿开采中的汞释放，以及由于森林砍伐和原始森林的燃烧，汞释放了甲基汞的天然沉积物，影响了当地的水生脊椎动物。这项研究报告了河豚海豚Inia和Sotalia的汞含量。分析了在Arauca和Orinoco河（哥伦比亚），Amazon河（哥伦比亚），Itenez河（玻利维亚）的支流和Tapajos河（巴西）的46个人身上采集的肌肉组织样品中的汞浓度。四种不同分类单元的肌肉组织中总汞（Hg）浓度的范围为：I. geoffrensis humboldtiana 0.003-3.99 mg kg^-1  ww（n  = 21，M _e  = 0.4），I. g。geoffrensis 0.1-2.6毫克千克^-1 湿重（Ñ  = 15，中号_È  = 0.55），I. boliviensis 0.03-0.4毫克千克^-1 湿重（Ñ  = 8，中号_È  = 0.1）和S. fluviatilis 0.1-0.87毫克公斤^-1  ww（n  = 2，M _e  = 0.5）。在奥里诺科河盆地获得在我们研究的最高汞含量，从一个少年男性记录一克 洪堡（3.99 mg kg ^-1 ww）。在亚马孙河流域，塔帕霍斯河（巴西）的成年雄性汞的汞含量更高。geoffrensis（2.6 mg kg ^-1  ww）和亚马逊河来自成年雌性S. fluviatilis（0.87 mg kg ^-1  ww）。我们的数据支持分布在整个评估盆地中的河豚体内总汞含量的存在，证明了这些鲸类动物作为前哨物种的角色，也是在自然水生环境中存在这种重金属的生物指示剂。