Biotechnology and Bioengineering Department, Center for Research and Advanced Studies (Cinvestav), Mexico City, Mexico.
The Environmental Biogeochemistry in Extreme Ecosystems Laboratory (EnBEELab), University of Magallanes, Punta Arenas, Chile.
Sci Rep. 2020 Feb 25;10(1):3423. doi: 10.1038/s41598-020-60394-8.
It is commonly assumed that methane (CH) released by lakes into the atmosphere is mainly produced in anoxic sediment and transported by diffusion or ebullition through the water column to the surface of the lake. In contrast to that prevailing idea, it has been gradually established that the epilimnetic CH does not originate exclusively from sediments but is also locally produced or laterally transported from the littoral zone. Therefore, CH cycling in the epilimnion and the hypolimnion might not be as closely linked as previously thought. We utilized a high-resolution method used to determine dissolved CH concentration to analyze a Siberian lake in which epilimnetic and hypolimnetic CH cycles were fully segregated by a section of the water column where CH was not detected. This layer, with no detected CH, was well below the oxycline and the photic zone and thus assumed to be anaerobic. However, on the basis of a diffusion-reaction model, molecular biology, and stable isotope analyses, we determined that this layer takes up all the CH produced in the sediments and the deepest section of the hypolimnion. We concluded that there was no CH exchange between the hypolimnion (dominated by methanotrophy and methanogenesis) and the epilimnion (dominated by methane lateral transport and/or oxic production), resulting in a vertically segregated lake internal CH cycle.
人们通常认为，湖泊向大气中释放的甲烷（CH）主要是在缺氧沉积物中产生的，并通过扩散或沸腾穿过水柱运输到湖泊表面。与普遍的观点相反，人们逐渐认识到，表水层的 CH 并非仅源自沉积物，而是也在当地产生或从湖滨区侧向运输而来。因此，表水层和下水层中的 CH 循环可能不像以前认为的那样紧密相关。我们利用一种高分辨率的方法来测定溶解 CH 的浓度，分析了一个西伯利亚湖泊，其中表水层和下水层的 CH 循环完全被水柱的一个区段隔开，该区段未检测到 CH。这个没有检测到 CH 的层远低于氧跃层和透光层，因此被认为是无氧的。然而，根据扩散-反应模型、分子生物学和稳定同位素分析，我们确定这个层吸收了沉积物中和下水层最深部分产生的所有 CH。我们得出结论，下水层（以甲烷氧化和甲烷生成为主）和表水层（以甲烷侧向运输和/或好氧生产为主）之间没有 CH 交换，导致湖泊内部 CH 循环垂直分隔。
