Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, Quebec City, QC G1K 9A9, Canada.
Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon (INPA), Manaus, AM 69067-375, Brazil.
Sci Total Environ. 2022 Oct 15;843:157032. doi: 10.1016/j.scitotenv.2022.157032. Epub 2022 Jun 30.
We investigated how natural dissolved organic matter (DOM) of the Rio Negro (Amazon) affects acute copper (Cu) toxicity to local fish: the cardinal tetra (Paracheirodon axelrodi) and the dwarf cichlid (Apistogramma agassizii). It is established that Cu complexation with DOM decreases Cu bioavailability (and thus toxicity) to aquatic organisms, as conceptualized by the Biotic Ligand Model (BLM). However, we also know that Rio Negro's DOM can interact with fish gills and have a beneficial effect on Na homeostasis, the main target of acute Cu toxicity in freshwater animals. We aimed to tease apart these potential protective effects of DOM against Cu-induced Na imbalances in fish. In the laboratory, we acclimated fish to Rio Negro water (10 mg L DOC) and to a low-DOM water (1.4 mg L DOC) with similar ion composition and pH (5.9). We measured 3-h Cu uptake in gills and unidirectional and net Na physiological fluxes across a range of Cu concentrations in both waters. Various DOM pre-acclimation times (0, 1 and 5 days) were evaluated in experiments with P. axelrodi. Copper exposure led to similar levels of net Na loss in the two fish, but with distinct effects on Na influx and efflux rates reflecting their different ionoregulation strategies. Rio Negro DOM protected against Cu uptake and toxicity in the two fish species. Both Cu uptake in fish gills and Na regulation disturbances were relatively well predicted by the modelled aqueous free Cu ion concentration. These findings suggest that protection by DOM occurs mainly from Cu complexation under the tested conditions. The prevalence of this geochemical-type protection over a physiological-type protection agrees with the BLM conceptual framework, supporting the use of the BLM to assess the risk of Cu in these Amazonian waters.
我们研究了里奥内格罗（亚马逊）天然溶解有机物（DOM）如何影响当地鱼类—— cardinal tetra（Paracheirodon axelrodi）和 dwarf cichlid（Apistogramma agassizii）的急性铜（Cu）毒性。众所周知，DOM 与 Cu 的络合作用会降低 Cu 对水生生物的生物利用度（因此降低毒性），这一概念被生物配体模型（BLM）所认可。然而，我们也知道，里奥内格罗的 DOM 可以与鱼类鳃相互作用，并对 Na 稳态产生有益影响，这是淡水动物急性 Cu 毒性的主要靶标。我们旨在厘清 DOM 对鱼类 Cu 诱导的 Na 失衡的潜在保护作用。在实验室中，我们使鱼类适应里奥内格罗河水（DOC 浓度为 10mg/L）和低 DOM 水（DOC 浓度为 1.4mg/L），这两种水的离子组成和 pH 值相似（pH 值为 5.9）。我们在这两种水中测量了 Cu 在鳃中的 3 小时摄取量，以及在一系列 Cu 浓度下 Na 的单向和净生理通量。在针对 P. axelrodi 的实验中，评估了不同的 DOM 预适应时间（0、1 和 5 天）。Cu 暴露导致两种鱼类的净 Na 损失水平相似，但对 Na 流入和流出率的影响不同，这反映了它们不同的离子调节策略。里奥内格罗 DOM 对两种鱼类的 Cu 摄取和毒性具有保护作用。鱼类鳃中的 Cu 摄取和 Na 调节紊乱都可以通过模型计算的游离 Cu 离子浓度很好地预测。这些发现表明，在测试条件下，DOM 的保护作用主要来自于 Cu 的络合作用。在这种地球化学类型的保护作用超过生理类型的保护作用的情况下，这与 BLM 的概念框架一致，支持使用 BLM 来评估这些亚马逊水域中 Cu 的风险。
