The Ephemeral Signature of Permafrost Carbon in an Arctic Fluvial Network
The Ephemeral Signature of Permafrost Carbon in an Arctic Fluvial Network
复制标题
DOI：
10.1029/2017jg004311
复制
发表时间：
2018-05-01
影响因子：
3.7
通讯作者：
Spencer, Robert G. M.
中科院分区：
文献类型：
--
作者：
Drake, Travis W.;Guillemette, Francois;Spencer, Robert G. M.
北极河流网络处理、排出和输送大量的陆地有机碳（C），特别是溶解有机碳（DOC）。然而，这些通量中的永冻层碳的比例受到很大的限制。多年冻土来源的DOC的量化的一个主要障碍是，它是快速呼吸，没有留下一个独特的示踪剂，它的存在。在这项研究中，我们调查了细菌呼吸二氧化碳（CO2;溶解无机碳测量; DIC）的生产过程中最大的夏末解冻在网站跨越河流网络（科雷马盆地，西伯利亚），以评估是否可以检测到永久冻土DOC的生物降解的持久性老化（C-14耗尽）签名的DIC池。使用Keeling图解释DIC产生的河水的生物孵化，我们表明，细菌呼吸不同来源的DOC通过河流网络向下游移动。只有在严重的冻土融化影响的网站检测到的永久冻土的呼吸（生产老化的CO2）。在nonpermafrost解冻影响的网站，环境DIC是现代的（C-14丰富），但不是排除呼吸的永冻OC上游，我们建议，C-14耗尽DIC是压倒现代DIC。通过傅里叶变换离子回旋共振质谱法溶解的有机物组成的调查强调，脂肪族和含氮化合物的水平升高与生产的老年DIC，提供分子水平的洞察力，为什么永冻层衍生的溶解的有机物迅速呼吸。总体而言，从这项研究的结果表明，追踪输入的高活性基板系统与不同的有机物来源的困难。
Arctic fluvial networks process, outgas, and transport significant quantities of terrestrial organic carbon (C), particularly dissolved organic carbon (DOC). The proportion of permafrost C in these fluxes, however, is poorly constrained. A primary obstacle to the quantification of permafrost-derived DOC is that it is rapidly respired without leaving a unique tracer of its presence. In this study, we investigated the production of bacterial respiratory carbon dioxide (CO2; measured as dissolved inorganic carbon; DIC) during maximum late-summer thaw in sites spanning a fluvial network (Kolyma Basin, Siberia) to assess whether the biodegradation of permafrost DOC could be detected by the presence of a persistent aged (C-14-depleted) signature on the DIC pool. Using Keeling plot interpretation of DIC produced in bioincubations of river water, we show that bacteria respire varying sources of DOC moving downstream through the fluvial network. Respiration of permafrost (production of aged CO2) was only detected in heavily permafrost thaw influenced sites. In nonpermafrost thaw impacted sites, ambient DIC was modern (C-14-enriched), but rather than precluding the respiration of permafrost OC upstream, we suggest that C-14-depleted DIC is overwhelmed by modern DIC. Investigation of dissolved organic matter composition via Fourier transform ion cyclotron resonance mass spectrometry highlighted that elevated levels of aliphatic and nitrogen-containing compounds were associated with the production of aged DIC, providing molecular-level insight as to why permafrost-derived dissolved organic matter is rapidly respired. Overall, results from this study demonstrate the difficulty of tracing inputs of a highly reactive substrate to systems with diverse organic matter sources.