Terrestrial carbon in aquatic ecosystems: experimental tests of the subsidy-stability hypothesis

生态系统在空间上由物质和能量的流动联系在一起。在过去的十年里，越来越多的人认识到，资源在景观上的移动可以补贴当地栖息地的人口。此外，理论表明，资源补贴可能起到稳定食物网和生态系统的作用，但这些预测在很大程度上仍未经检验。本研究旨在探讨陆源溶解有机碳（DOC）对水生生态系统代谢稳定性的影响。传统上被认为是一种低质量的资源，现在人们认识到，陆地DOC输入是细菌的一种资源补贴，可以决定接收水生生态系统是作为大气二氧化碳的来源还是汇。该项目的第一个目标是通过一组操纵陆地DOC供应率的全池实验来描述补贴-稳定关系的形状、大小和方向。该项目的第二个目标是确定陆地DOC影响水生生态系统稳定性的机制。具体而言，该项目将评估DOC是否通过改变营养循环、改变温度动态或改变不同微生物群之间的相互作用强度来影响生态系统的稳定性。该项目的目标将使用自主传感器技术来量化生态系统代谢和温度变化，放射性同位素分析来测量营养循环，分子技术来评估微生物群落代谢活动的变化。在全球范围内，由于大气沉积、气候变率和土地利用转移等综合因素，陆地DOC向水生生态系统的输出正在增加。本提案中开发的工具和方法将解决这一现象，并帮助科学家和管理者预测在现有和未来气候情景下DOC负荷的变化如何影响生态系统功能和水质。该项目具有重要的教育和推广组成部分，将促进凯洛格生物站（KBS）、密歇根州立大学（MSU）和密歇根州农村K-12学区之间的互动。具体而言，该项目将继续开展一项正在进行的合作，将生态稳定性、微生物多样性和生物地球化学循环的概念引入高中课堂。该项目还将为本科生、研究生、高中教师和博士后研究员提供生态系统科学、定量生态学和分子生物学领域的跨学科研究培训。

Ecosystems are spatially linked by the flux of materials and energy. Over the past decade there has been growing appreciation that the movement of resources across the landscape can act to subsidize populations in local habitats. In addition, theory suggests that resource subsidies may act to stabilize food webs and ecosystems, but these predictions remain largely untested. This study will examine the effects of terrestrial-derived dissolved organic carbon (DOC) on the stability of aquatic ecosystem metabolism. Traditionally been viewed as a low quality resource, it is now recognized that terrestrial DOC inputs are a resource subsidy for bacteria that can determine whether recipient aquatic ecosystems function as sources or sinks of atmospheric carbon dioxide. The first goal of this project is to describe the shape, magnitude, and direction of subsidy-stability relationships using a set of whole-pond experiments that manipulate the supply rate of terrestrial DOC. The second goal of this project is to identify the mechanisms by which terrestrial DOC influences aquatic ecosystem stability. Specifically, the project will assess whether DOC affects ecosystem stability by modifying nutrient cycling, altering temperature dynamics, or by altering interaction strengths among different groups of microorganisms. The objectives of this project will be assessed using a combination of autonomous sensor technology to quantify ecosystem metabolism and temperature variability, radioisotope assays to measure nutrient cycling, and molecular techniques to evaluate changes in the metabolic activity of microbial communities. At a global scale, the export of terrestrial DOC to aquatic ecosystems is increasing due to a combination of factors, including atmospheric deposition, climate variability, and shifting land use. The tools and approaches developed in this proposal will address this phenomenon and help scientists and managers predict how changes in DOC loading affect ecosystem functioning and water quality under existing and future climate scenarios. This project has a significant education and outreach component that will foster interactions among the Kellogg Biological Station (KBS), Michigan State University (MSU), and rural Michigan K-12 school districts. Specifically, the project will continue an ongoing collaboration that will introduce concepts of ecological stability, microbial diversity, and biogeochemical cycling into the high-school classroom. The project will also provide interdisciplinary research training in the fields of ecosystem science, quantitative ecology, and molecular biology for undergraduate students, a graduate student, a high school teacher, and postdoctoral researcher.