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Abstract：
To assess how the quality and properties of the natural dissolved organic carbon (DOC) could drive different effects on gill physiology, we analysed the ionoregulatory responses of a native Amazonian fish species, the tambaqui Colossoma macropomum, to the presence of dissolved organic carbon (DOC; 10 mg l-1 ) at both pH 7.0 and pH 4.0 in ion-poor water. The DOC was isolated from black water from São Gabriel da Cachoeira (SGC) in the upper Rio Negro of the Amazon (Brazil) that earlier been shown to protect a non-native species, zebrafish Danio rerio against low pH under similar conditions. Transepithelial potential (TEP), net flux rates of Na+ , Cl- and ammonia and their concentrations in plasma and Na+ , K+ ATPase; v-type H+ ATPase and carbonic anhydrase activities in gills were measured. The presence of DOC had negligible effects at pH 7.0 apart from lowering the TEP, but it prevented the depolarization of TEP that occurred at pH 4.0 in the absence of DOC. However, contrary to our initial hypothesis, SGC DOC was not protective against the effects of low pH. Colossoma macropomum exposed to SGC DOC at pH 4.0 experienced greater net Na+ and Cl- losses, decreases of Na+ and Cl- concentrations in plasma and elevated plasma ammonia levels and excretion rates, relative to those exposed in the absence of DOC. Species-specific differences and changes in DOC properties during storage are discussed as possible factors influencing the effectiveness of SGC DOC in ameliorating the effects of the acid exposure.
摘要：
为了评估天然溶解有机碳（DOC）的质量和特性如何对g生理产生不同的影响，我们分析了一种本地亚马逊鱼类的离子调节反应，tambaqui大型巨像，在pH7.0和pH4.0的贫离子水中都存在溶解的有机碳（DOC；10mgl-1）。DOC是从亚马逊（巴西）上RioNegro的圣加布里埃尔·达·卡乔埃拉（SGC）的黑水中分离出来的，该黑水较早被证明可以保护非本地物种，斑马鱼Daniorerio在相似条件下对抗低pH。跨上皮电位(TEP),Na+的净通量率，Cl-和氨及其在血浆和Na+中的浓度，测量了KATPase；g中的v型HATPase和碳酸酐酶活性。在pH7.0时，DOC的存在除了降低TEP，但是它可以防止在没有DOC的情况下在pH4.0下发生的TEP去极化。然而,与我们最初的假设相反，SGCDOC对低pH的影响没有保护作用。在pH4.0下暴露于SGCDOC的大型巨像瘤经历了更大的净Na+和Cl-损失，血浆中Na+和Cl-浓度降低，血浆氨水平和排泄率升高，相对于在没有DOC的情况下暴露的那些。讨论了物种特异性差异和储存过程中DOC特性的变化，作为影响SGCDOC改善酸暴露效果的可能因素。
