Factors controlling seasonal changes in the structure and function of food webs of perennial spring streams in Arctic Alaska

这项研究将调查在阿拉斯加北方春季河流营养循环。在阿拉斯加北坡东部，常年流动的春季河流和接近恒定的水温（3- 7摄氏度）相对广泛，其他源头河流一年中有六个多月冻结。其中一个驱动假设是，由于温度几乎全年保持不变，异养生物活动的速率（例如，次级生产，生态系统呼吸）在夏季和冬季之间不会有差异。然而，初级生产率将受到光照的限制，因此由于极端的日长年度周期（24小时光照到24小时黑暗），季节之间会有很大的差异，可能会迫使相关生态过程的周期。此外，越冬鱼（北方多莉瓦登焦红点鲑malma）的迁移运动和春天的溪流假设影响捕食率和营养供应。因此，移徙模式是会进一步加剧群落和生态系统动态的季节性模式的过程。这些假设主要是基于外推的夏季结构和过程的假设冬季条件下，没有冬季观测的好处。本研究的第一个目标是通过将生态系统代谢、分解速率、大型无脊椎动物群落结构和生产与潜在的非生物驱动因素联系起来，来测试调查生物活动的季节性变化。在两年的时间里，将在一条具有代表性的春季溪流中进行大约每月一次的实验。本研究的第二个目标是分离的假设的后果，从其他驱动程序的鱼迁移有关焦人口结构，生产，捕食和营养排泄率观察到的生物生产力的模式。拟议的研究将为预测了解北极春季生态系统潜在的不成比例的景观作用提供基础，这些生态系统季节性地从该地区流动溪流栖息地的1%转移到100%。这两个目标的结果将结合起来，以评估春季流的作用之间的相互作用，作为“热点”的全年生物生产力和分类丰富性，和迁移的焦人口，其运动连接春季流的水生生态系统在整个北坡景观，从布鲁克斯范围沿海博福特海。该项目将通过与北极国家野生动物保护区（ANWR）的科学伙伴关系造福社会。北坡未来的温度和降水模式的预测表明，理解的作用，常年春天的季节性避难所流社区可能被证明是至关重要的未来管理的淡水资源的ANWR。该项目还将通过两项主要活动促进教学、培训和学习，将研究与教育结合起来。首先，一个博士。学生和一名博士后研究助理将接受培训，作为这个项目的一部分。第二，本科生将参与实验室活动和夏季REU支持将寻求本科生参加夏季实地考察工作，在此期间，他们将开发与本项目相关的独立研究。

This research will investigate nutrient cycling in spring-fed streams in northern Alaska. Spring-fed streams with perennial flow and near-constant water temperatures (3- 7oC) are relatively widespread on the eastern North Slope of Alaska, where other headwater streams freeze solid for more than six months of the year. One of the driving hypotheses is that, because temperatures remain nearly constant year-round, rates of heterotrophic biological activity (e.g., secondary production, ecosystem respiration) will not differ between the summer and winter. Rates of primary production, however, will be limited by light and so will differ dramatically between seasons due to extreme annual cycles in day length (24-h light to 24-h darkness), potentially forcing cycles in related ecological processes. Additionally, the migratory movement of overwintering fish (northern Dolly Varden char Salvelinus malma) in and out of spring streams is hypothesized to affect predation rates and nutrient supply. Therefore, migration patterns are processes that should further exacerbate seasonal patterns of community and ecosystem dynamics. These hypotheses are based largely on the extrapolation of summer structure and processes to assumed winter conditions, without the benefit of winter observations. The first objective of this study is to test investigate seasonal changes in biological activity by relating ecosystem metabolism, decomposition rates, and macroinvertebrate community structure and production to potential abiotic drivers. Experiments will be coducted approximately monthly in a single, representative spring stream over a two-year period. The second objective of the study is to separate the hypothesized consequences of fish migration from other drivers by relating char population structure, production, and rates of predation and nutrient excretion to observed patterns of biological productivity. The proposed research will provide the basis for a predictive understanding of the potentially disproportionate landscape role of Arctic spring ecosystems, which shift seasonally from being 1% to 100% of the region's flowing stream habitat. The results of the two objectives will be combined to assess interactions between the role of spring streams as "hot spots" of year-round biological productivity and taxonomic richness, and that of migratory char populations, the movements of which connect spring streams to aquatic ecosystems across the whole North Slope landscape, from the Brooks Range to the coastal Beaufort Sea. This project will benefit society through a scientific partnership with the Arctic National Wildlife Refuge (ANWR). Predictions of future patterns of temperature and precipitation on the North Slope suggest that understanding of the role of perennial springs as seasonal refugia for stream communities may prove critical to future management of the freshwater resources of ANWR. This project will also integrate research and education by promoting teaching, training, and learning through two primary activities. First, one Ph.D. student and one Postdoctoral Research Associate will receive training as part of this project. Second, undergraduate students will be involved in laboratory activities and summer REU support will be sought for undergraduates to join summer fieldwork efforts, during which they will develop independent research related to this project.