了解溶解有机物生物地球化学通过<em>原位</em>在河流生态系统营养手法
Summary
溶解有机物提供能量和营养流生态系统的一个重要来源。在这里，我们展示了一个基于现场的方式，通过很容易复制的营养脉冲操纵原位溶解有机物环境池。
Abstract
Dissolved organic matter (DOM) is a highly diverse mixture of molecules providing one of the largest sources of energy and nutrients to stream ecosystems. Yet the in situ study of DOM is difficult as the molecular complexity of the DOM pool cannot be easily reproduced for experimental purposes. Nutrient additions to streams however, have been shown to repeatedly alter the in situ and ambient DOM pool. Here we demonstrate an easily replicable field-based method for manipulating the ambient pool of DOM at the ecosystem scale. During nutrient pulse experiments changes in the concentration of both dissolved organic carbon and dissolved organic nitrogen can be examined across a wide-range of nutrient concentrations. This method allows researchers to examine the controls on the DOM pool and make inferences regarding the role and function that certain fractions of the DOM pool play within ecosystems. We advocate the use of this method as a technique to help develop a deeper understanding of DOM biogeochemistry and how it interacts with nutrients. With further development this method may help elucidate the dynamics of DOM in other ecosystems.
Introduction
溶解有机物质（DOM）提供了一个重要的能量和营养源的淡水的生态系统和被定义为通过0.7微米的过滤器通过有机物。在水生生态系统，DOM也能影响光衰减和金属络合。 DOM是具有各种官能团的有机化合物，以及必需的营养物质，如氮（N）和磷（P）的高度多样化和不均匀混合物。而“DOM”介绍，包括其C，N和P分量整个池，其浓度作为溶解有机碳（DOC）测定。在DOM池固有的复杂分子然而，造成其研究的挑战。例如，有测量由有机营养物如溶于有机氮（DON）和可溶性有机磷（DOP）的总的DOM池的分数没有直接的方法。相反，有机营养的浓度必须通过差来确定（ <em>如：[DON] = [总溶解氮] – [无机氮]）。
添加一个现实的DOM修正案到流是困难的，因为环境的DOM池的多样性。以前的研究已经加入单一碳源（ 如葡萄糖，尿素1） 或如落叶层渗滤液2特定源来操纵在外地的浓度。不过，这些来源不是特别有代表性的环境DOM池。试图缩小或集中用于随后的实验环境的DOM也造成了困难，包括某些馏分（ 如高度不稳定分量）的处理过程中的损失。其结果是，它是很难理解的周围的DOM池对照，因为我们目前不具备任何方法直接操作环境的DOM池。然而，由于DOM的生物地球化学被链接到在环境中常见的营养物质（ 例如尼特率[NO 3 – 3），我们可以添加其他溶质流生态系统和测量DOM池这些操作的响应。通过检查DOM池如何响应广泛的实验实行营养浓度，我们希望能够更加深入地了解DOM如何应对波动的环境条件。
在流生物地球化学常用的一种方法是在营养物添加方法。营养除了实验历来被用来理解吸收动力学或添加溶质4,5,6,7的命运。营养增补可以是对小时6天标尺4，或长期操作过的多个年8过程的短期。营养增补还可以包括同位素标记的营养素（ 例如 ，15 N-NO 3 – ）通过生物地球化学反应来跟踪添加营养素。然而，基于同位素研究往往EXPEnsive并要求多个底栖车厢，其中同位素标记的营养素可以保留的具有挑战性的分析（ 如消化）。最近的实验揭示了短期脉冲营养素的效用阐明非加和环境溶质，如DOM 9,10对照，揭示由检查原位生物地球化学反应实时的新方法。在这里，我们描述和证明密钥的方法步骤，以了解C，N及具体的控制的耦合生物地球化学的高度多样化的DOM池的目标进行短期养分脉冲。此容易再现方法包括添加营养脉冲的实验流达到并测量在这两个操纵溶质和感兴趣的响应变量（ 如 DOC，DON，DOP）的浓度变化。 通过原位直接操纵营养物浓度，我们能够间接改变DOM游泳池和检查跨越营养浓度10的动态范围DOM浓度如何变化的。
Protocol
Representative Results
Discussion
营养脉冲方法的目的，如这里提出，是表征和量化环境流水DOM的高度多样化池的两端一个附加的无机养分的动态范围的响应。如果添加溶质充分提高了反应溶质的浓度，大的推理空间可以创建理解DOM的生物地球化学循环如何链接到营养浓度。这种营养脉冲的方法是理想的，因为它涉及无用高原式加成相关联的机械的（ 例如蠕动泵），并且不涉及昂贵同位素技术。这些操作是容易复制和多种…
Declarações
The authors have nothing to disclose.
Acknowledgements
The authors acknowledge the Water Quality Analysis Laboratory at the University of New Hampshire for assistance with sample analysis. The authors also thank two anonymous reviewers whose comments have helped to improve the manuscript. This work is funded by the National Science Foundation (DEB-1556603). Partial funding was also provided by the EPSCoR Ecosystems and Society Project (NSF EPS-1101245), New Hampshire Agricultural Experiment Station (Scientific Contribution #2662, USDA National Institute of Food and Agriculture (McIntire-Stennis) Project (1006760), the University of New Hampshire Graduate School, and the New Hampshire Water Resources Research Center.
Materials
| Sodium Nitrate | Any | Any | |
| Sodium Chloride | Any | Any | Store purchased table salt can be used as well, however, it does contain trace levels of impurities |
| Whatman GFF glass-fiber filters | Any | Any | |
| BD Filtering Syringe | Any | Any | |
| EMD Millipore Swinnex Filter Holders | Any | Any | |
| Syringe stop-cock | Any | Any | |
| YSI Multi-parameter probe | Yellow Springs International | 556-01 | |
| Wide mouth HDPE 125 ml bottles | Any | Any | |
| 60 ml HDPE bottles | Any | Any | |
| 20 L bucket | Any | Any | |
| Field measuring tape | Any | Any | |
| Lab labeling tape | Any | Any | |
| Stir stick | Any | Any | |
| Cooler | Any | Any | |
| Sharpie pen | Any | Any | |
| Field notebook | Any | Any | |
| Tweezers | Any | Any | |
| Zip-lock bags | Any | Any |
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