Abstract：
The Rio Negro basin of Amazonia (Brazil) is a hotspot of fish biodiversity that is under threat from copper (Cu) pollution. The very ion-poor blackwaters have a high dissolved organic carbon (DOC) concentration. We investigated the Cu sensitivity of nine Amazonian fish species in their natural blackwaters (Rio Negro). The acute lethal concentration of Cu (96 h LC50) was determined at different dilutions of Rio Negro water (RNW) in ion-poor well water (IPW), ranging from 0 to 100%. The IPW was similar to RNW in pH and ionic composition but deficient in DOC, allowing this parameter to vary 20-fold from 0.4 to 8.3 mg/L in tests. The Biotic Ligand Model (BLM; Windward version 3.41.2.45) was used to model Cu speciation and toxicity over the range of tested water compositions, and to estimate lethal Cu accumulations on the gills (LA50). The modeling predicted a high relative abundance of Cu complexes with DOC in test waters. As these complexes became more abundant with increasing RNW content, a concomitant decrease in free Cu2+ was observed. In agreement with this modeling, acute Cu toxicity decreased (i.e. 96 h LC50 values increase) with increasing RNW content. The three most sensitive species (Hemigrammus rhodostomus, Carnegiella strigatta and Hyphessobrycon socolofi) were Characiformes, whereas Corydoras schwartzi (Siluriformes) and Apistogramma agassizii (Cichliformes) were the most tolerant. These sensitivity differences were reflected in the BLM-predicted lethal gill copper accumulation (LA50), which were generally lower in Characiformes than in Cichliformes. Using these newly estimated LA50 values in the BLM allowed for accurate prediction of acute Cu toxicity in the nine Amazonian fish. Our data emphasize that the BLM approach is a promising tool for assessing Cu risk to Amazonian fish species in blackwater conditions characterized by very low concentrations of major ions but high concentrations of DOC.
摘要：
亚马逊（巴西）的里约内格罗盆地是鱼类生物多样性的热点，受到铜（Cu）污染的威胁。非常缺乏离子的黑水具有很高的溶解有机碳(DOC)浓度。我们调查了9种亚马逊鱼类在其天然黑水（RioNegro）中的铜敏感性。在贫离子井水（IPW）中不同稀释度的RioNegro水（RNW）确定了Cu的急性致死浓度（96hLC50），范围从0到100%。IPW在pH和离子组成上与RNW相似，但缺乏DOC，允许此参数在测试中从0.4到8.3mg/L变化20倍。生物配体模型（BLM；迎风版本3.41.2.45）用于在测试的水组成范围内对Cu形态和毒性进行建模，并估计g上的致命铜积累（LA50）。该模型预测了测试水中具有DOC的Cu配合物的相对丰度较高。随着RNW含量的增加，这些复合物变得越来越丰富，观察到游离Cu2+的伴随减少。与这个模型一致，随着RNW含量的增加，急性Cu毒性降低（即96hLC50值增加）。三个最敏感的物种(Hemigrammusrhodostomus，短发Carnegiella和Hyphessobryconsocolofi）是Characiformes，而Corydorasschwartzi（Siluriformes）和Apistogrammaagassizii（Cichliformes）最耐受。这些敏感性差异反映在BLM预测的致死g铜积累（LA50）中，Characiformes的含量通常低于Cichliformes。在BLM中使用这些新估计的LA50值可以准确预测9条亚马逊鱼中的急性Cu毒性。我们的数据强调，BLM方法是评估黑水条件下亚马逊鱼类物种的铜风险的有前途的工具，黑水条件的主要离子浓度非常低，但DOC浓度高。
