As climate-driven El Niño Southern Oscillation (ENSO) events are projected to increase in frequency and severity, much attention has focused on impacts regarding ecosystem productivity and carbon balance in Amazonian rainforests, with comparatively little attention given to carbon dynamics in fluvial ecosystems. In this study, we compared the wet 2012 La Niña period to the following normal hydrologic period in the Amazon River. Elevated water flux during the La Niña period was accompanied by dilution of inorganic ion concentrations. Furthermore, the La Niña period exported 2.77 Tg C yr⁻¹ more dissolved organic carbon (DOC) than the normal period, an increase greater than the annual amount of DOC exported by the Mississippi River. Using ultra-high-resolution mass spectrometry, we detected both intra- and interannual differences in dissolved organic matter (DOM) composition, revealing that DOM exported during the dry season and the normal period was more aliphatic, whereas compounds in the wet season and following the La Niña event were more aromatic, with ramifications for its environmental role. Furthermore, as this study has the highest temporal resolution DOM compositional data for the Amazon River to-date we showed that compounds were highly correlated to a 6-month lag in Pacific temperature and pressure anomalies, suggesting that ENSO events could impact DOM composition exported to the Atlantic Ocean. Therefore, as ENSO events increase in frequency and severity into the future it seems likely that there will be downstream consequences for the fate of Amazon Basin-derived DOM concurrent with lag periods as described here.

中文翻译：

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亚马逊河有机分子特征的驱动因素

由于气候驱动的厄尔尼诺南方涛动 (ENSO) 事件的频率和严重程度预计会增加，因此人们越来越关注亚马逊雨林生态系统生产力和碳平衡的影响，而对河流生态系统中碳动态的关注相对较少。在这项研究中，我们将 2012 年潮湿的拉尼娜现象与亚马逊河接下来的正常水文时期进行了比较。拉尼娜现象期间水通量的升高伴随着无机离子浓度的稀释。此外，拉尼娜时期出口了 2.77 Tg C yr ^-1溶解有机碳 (DOC) 比正常时期多，增幅大于密西西比河每年出口的 DOC 量。使用超高分辨率质谱，我们检测到溶解有机质 (DOM) 成分的年内和年际差异，揭示在旱季和正常时期输出的 DOM 更富含脂肪，而在雨季和以下的化合物拉尼娜事件更加芳香，对其环境作用产生了影响。此外，由于这项研究拥有迄今为止亚马逊河时间分辨率最高的 DOM 成分数据，我们表明化合物与太平洋温度和压力异常的 6 个月滞后高度相关，这表明 ENSO 事件可能会影响出口到其他地区的 DOM 成分。大西洋。所以，