Collaborative Research: Landscape Limnology of Mountain Watersheds: Nutrient Retention and Ecosystem Stability in Complex Aquatic Ecosystems

犹他州立大学的Wayne Wurtsaugh和Michelle Baker与蒙大拿州立大学的Brian McGlynn合作。通过复杂的流域进行营养运输是一个重要的科学和管理问题，必须了解这一问题，以便社会能够做出适当的管理决策，以应对威胁我们水体的日益严重的大气和农业污染。大多数关于营养物质运输的研究都集中在分水岭的单一组成部分，如河流或湖泊，但对分水岭中存在的河流和湖泊的组合如何影响这些过程知之甚少。我们的工作将研究湖泊、湖底(滨海区)、溪流及其地下成分(潜流带)之间的相互作用如何影响爱达荷州锯齿山脉流域的氮素运输。我们认为，在没有湖泊或高度发达的浅水地带的简单流域，营养物质在春季积雪融化时会迅速径流，因此夏季后期几乎没有什么可以为水生植物(浮游植物、附生植物)的生长提供动力。然而，我们预计，在有许多湖泊的复杂流域，氮的春季脉冲将受到抑制，从而提供比简单流域更稳定的这种养分供应。如果养分输送得到稳定，我们预计浮游植物和附生植物的生长也将受到较少的冲击，从而增加生态系统的稳定性。我们将通过使用氮的稳定同位素(15N)在小空间尺度上测量营养物质的移动来检验这些想法，使用这些速率来模拟营养物质如何在整个流域内发生转移，然后用全排水示踪实验以及湖泊和溪流中营养物质通量和藻类生长的大规模流域测量来检验我们的模型预测。为了扩大我们工作的影响，我们将与教育工作者合作，为小学生开发课程，并为基于网络的学习提供模块。

Wayne Wurtsaugh & Michelle Baker, Utah State University in collaboration with, Brian McGlynn, Montana State University.Nutrient transport through complex watersheds is an important scientific and management problem that must be understood so that society can make appropriate management decisions to deal with the increasing levels of atmospheric and agricultural pollution threatening our water bodies. Most studies of nutrient transport have focused on single components of the watershed such as a stream or lake, but little is know about how combinations of streams and lakes that exist in watersheds influence these processes. Our work will address how interacting complexes of lakes, lake bottoms (littoral zones), streams, and their subsurface component (hyporheic zones) interact to influence nitrogen transport through watersheds in the Sawtooth Mountains of Idaho. We suggest that in simple watersheds without lakes or highly developed hyporheic zones, nutrients will runoff quickly during spring snowmelt so that little is left to fuel the growth of aquatic plants (phytoplankton, periphyton) latter in the summer. However, we expect that in complex watersheds with many lakes, the spring pulse of nitrogen will be dampened, thus providing a more stable supply of this nutrient than in simple watersheds. If nutrient delivery is stabilized, we expect that growth of phytoplankton and periphyton will also be less pulsed and thus increase ecosystem stability. We will test these ideas by measuring nutrient movement at small spatial scales with the stable isotope of nitrogen (15N), using those rates to model how nutrient transport occurs within whole watersheds, and then testing our model predictions with a whole-drainage tracer experiment and with large-scale watershed measurements of nutrient flux and algal growth in lakes and streams. To broaden the impact of our work, we will collaborate with educators to develop curricula for elementary school children, and make modules available for web-based learning.