Source Switching Maintains Dissolved Organic Matter Chemostasis Across Discharge Levels in a Large Temperate River Network
Source Switching Maintains Dissolved Organic Matter Chemostasis Across Discharge Levels in a Large Temperate River Network
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DOI：
10.1007/s10021-020-00514-7
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发表时间：
2020-06
期刊：
影响因子：
3.7
通讯作者：
J. Hosen;K. Aho;J. Fair;E. Kyzivat;S. Matt;J. Morrison;A. Stubbins;L. Weber;B. Yoon;P. Raymond
中科院分区：
文献类型：
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作者：
J. Hosen;K. Aho;J. Fair;E. Kyzivat;S. Matt;J. Morrison;A. Stubbins;L. Weber;B. Yoon;P. Raymond
溶解性有机物（DOM）对水生生态系统的结构和功能起调节作用。在小河流中，DOM浓度受陆地物质向水道的输送控制，因此变化很大。随着河流变大，河流连续体概念假设内部初级生产是一个越来越重要的DOM来源，但直接证据有限。最近，脉冲分流概念（Pulse-Shunt Concept）假设较大河流中的陆地DOM浓度随着流量和温度的增加而增加，这似乎与之前报道的大河中DOM的化学平衡相矛盾。本研究估算了2015年至2017年康涅狄格河流域（流域面积0.4-25,019平方公里）13条溪流和河流的日初级生产总值（GPP）。在温带大河中，DOM浓度的化学平衡是通过从低流量的本地DOM源转换到高流量的陆地DOM源来维持的，在较小的支流中，这种转换程度较低。在低流量时，与水生GPP相关的原生DOM是大型河流DOM库的主导部分。这种原生DOM维持主干和上游的化学平衡。因此，在较大的河流中，低流量的本地生产在夏季稳定了DOM浓度，而夏季是河流生态的关键时期。与脉冲分流概念一致，在高流量时期，陆源DOM是DOM的主要部分，大约70%的年流向海岸的DOM是陆源的。这种DOM转换模式可能在温带流域广泛存在，对内陆水域和沿海生态系统都有影响。
Dissolved organic matter (DOM) helps regulate aquatic ecosystem structure and function. In small streams, DOM concentrations are controlled by transport of terrestrial materials to waterways, and are thus highly variable. As rivers become larger, the River Continuum Concept hypothesizes that internal primary production is an increasingly important DOM source, but direct evidence is limited. Recently, the Pulse-Shunt Concept postulated that terrestrial DOM concentrations in larger rivers increase with flow and temperature, which seemingly contradicts previously reported DOM chemostasis in large rivers. This study estimates daily gross primary production (GPP) in 13 streams and rivers across the Connecticut River watershed (watershed areas 0.4–25,019 km2) from 2015 through 2017. Chemostasis of DOM concentrations is maintained by a switch from autochthonous sources of DOM at low flows to terrestrial sources of DOM at high flows in a large temperate river and to a lesser degree in smaller tributaries. At low flow, autochthonous DOM linked to aquatic GPP is the dominant fraction of the DOM pool in large rivers. This autochthonous DOM maintains chemostasis in the main stem and to a lesser extent upstream. Thus, in larger rivers, low-flow autochthonous production stabilizes DOM concentrations during the summer, a critical time for riverine ecology. Consistent with the Pulse-Shunt Concept, terrigenous DOM is the dominant fraction of DOM during higher flow periods and about 70% of annual DOM fluxes to the coast are terrestrial. This pattern of DOM switching is potentially widespread in temperate watersheds with implications to both inland waters and coastal ecosystems.