| Summary: | 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 conducted 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 PhD 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. Funding Source and Grant Number: NSF OPP-ANS 0611995 Investigator(s): Alexander D. Huryn and Jonathan P. Benstead Sponsor: University of Alabama Tuscaloosa, 801 University Blvd. Tuscaloosa, AL 35487
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