Collaborative Resarch: Terrestrial Support of Lake Food Webs: A Multi-Isotope Approach

该奖项根据2009年《美国恢复和再投资法》(公法111-5)提供资金。对生态系统中动物的支持最终来自两个来源：生态系统内的初级生产(例如，新生长的植物材料)或从其他生态系统进口的初级生产(例如，陆地材料输入到水生系统)。在湖泊中，众所周知，与内部初级生产相比，外部投入是很大的，但这些材料如何支持湖泊食物网的记录较少。氚是氢的稳定同位素，陆生和水生初级生产者的氢含量有很大差异。碳和氮的稳定同位素比率，虽然对比不是很好，但当与氢结合在一起时，也有助于区分消费者支持的来源。因此，对氢、碳和氮稳定同位素的综合分析可以区分湖泊动物和微生物使用内部和外部初级生产。在这项提议中，PIs将使用稳定同位素碳、氮和氢的测量以及一种新的建模方法来测试关于水生消费者陆地补贴的变化以及这些变化如何在不同类型的湖泊中变化的假设。多同位素方法还将应用于全湖营养施肥实验，以测试外部有机物对底栖和远洋消费者的支持差异。这项研究将直接衡量外部材料对消费者支持的差异，并有助于理解这些过程中生态系统之间差异的驱动因素。几名本科生和两名研究生将通过这项研究接受生态系统生态学、湖泊学、建模和稳定同位素方法学方面的培训。这项研究的结果将直接有助于私人投资机构教授的课程。将在这项研究中使用的稳定同位素模型将是其他研究人员感兴趣的工具。在开放获取软件上运行的模型将通过我们的网站以及文档、教程和测试数据提供。此外，私营部门还提议在关于同位素研究建模方法的全国会议上主办一个为期半天的讲习班。向更大的研究界提供多同位素模型方法将是该项目更广泛影响的一个重要组成部分。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The support of animals in ecosystems ultimately comes from two sources: primary production within an ecosystem (e.g. newly grown plant material) or primary production imported from other ecosystems (e.g. inputs of terrestrial material to an aquatic system). In lakes, it is well known that external inputs are large compared to internal primary production, but how these materials support lake food webs is less well documented. Deuterium is a stable isotope of hydrogen and deuterium content of terrestrial and aquatic primary producers is significantly different. Carbon and nitrogen stable isotope ratios, while less well contrasted, are also helpful, when coupled with deuterium, in discriminating sources of consumer support. Thus, integrated analysis of hydrogen, carbon and nitrogen stable isotopes can distinguish the use of internal versus external primary production by lake animals and microbes. In this proposal the PIs will use measurements of the stable isotopes carbon, nitrogen, and hydrogen along with a new modeling approach to test hypotheses about variation in terrestrial subsidies of aquatic consumers and how these vary among different types of lakes. The multi-isotope approach will also be applied to a whole lake nutrient fertilization experiment to test differences in the support of benthic versus pelagic consumers by external organic matter. This research will directly measure variation in the support of consumers by external materials and contribute to understanding the drivers of variation among ecosystems in these processes. Several undergraduates and 2 graduate students will receive training through this research in ecosystem ecology, limnology, modeling, and stable isotope methodology. Results from this research will contribute directly to courses taught by the PIs. The stable isotope model to be utilized in this study is a tool that will be of interest to other researchers. The model which runs on open access software will be made available through our website along with documentation, tutorials, and test data. In addition, the PIs propose to sponsor a half-day workshop at a national meeting on modeling methods in isotopic studies. Providing a multi-isotope model approach to the larger research community will be a significant component of the Broader Impacts of this project.