Grant: $228,020 - National Science Foundation - Jul. 14, 2009
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Award Description: This project is supported by the National Science Foundation and as such as two components: Intellectual Merit (the scientific research to be conducted) and Broader Impacts (which includes the educational, outreach and benefits to science and society of these activities. Intellecual Merit: Organic matter supporting consumers ultimately comes from two sources: primary production within an ecosystem (autochthonous sources) or primary production imported from other ecosystems (allochthonous sources). Allochthonous subsidies can decouple consumers from the constraints of internal primary production, thereby altering predator-prey interactions, nutrient cycling, and entire food webs. In lakes, it is well known that allochthonous inputs are important to both the carbon balance and whole-system metabolism. The importance of allochthonous inputs as subsidies to lake food webs is less well documented, a topic of keen interest, and, to date, difficult to measure. In prior research, significant progress was made by labeling entire lakes with inorganic carbon-13 (13C) to augment the isotopic contrast between terrestrial and aquatic sources. This approach has shortcomings: 1) experiments are limited to a few systems because of expense and logistics; and 2) only primary production that occurs during the labeling period is enriched with 13C. Thus, detrital autochthonous material due to primary production in previous seasons or years ('old autochthonous C ) may be indistinguishable from terrestrial sources. Deuterium, an isotope of hydrogen, resolves this problem because at ambient levels, it contrasts strongly between terrestrial and aquatic primary producers. Carbon and nitrogen stable isotope ratios, while less powerful, are also helpful, when coupled with deuterium, in discriminating sources of consumer support. Thus, integrated analysis of hydrogen, carbon and nitrogen stable isotopes reveals sources of organic matter without the need for whole lake-labeling experiments. In this proposal the PIs will use measurements of the natural abundances of carbon, nitrogen, and hydrogen isotopes along with a new Bayesian mixing model approach to test hypotheses about variation in terrestrial subsidies among consumers and across the landscape. The multi-isotope approach will also be applied to a whole lake nutrient enrichment manipulation to test differences in the support of benthic versus pelagic consumers by allochthonous organic matter and to evaluate the significance of 'old autochthonous C especially for benthic food webs. To date, variation of consumer biomass in ecosystems has been based on differences among systems in primary production, relative nutrient availability, predatory control, and other factors. Yet, the importance of detritus and exogenous materials for consumers has been long recognized and repeatedly stressed in ecological reviews. This research will directly measure variation in the support of consumers by exogenous materials and contribute to understanding the drivers of variation among ecosystems in these processes. Broader Impacts - 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 Bayesian isotope model utilized in this study is a tool that will be of interest to other researchers. The model which runs on open-source 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 using Bayesian methods in isotopic studies. Providing the multi-isotope model approach to the larger research community will be a significant component of the Broader Impacts of this project.
Project Description: Quarterly Activities. Our part of this project began on 15 September 2009. Thus, most of our activities are those to get ready for the bulk of the work. We have hired 10% of a Research Support Specialist (Mt. David Fischer) who will be engaged with the lab analyses generated by this project. We have made arrangements for this NSF grant to start paying 8.33% of Dr. Cole’s salary (one month of effort). The entire group of collaborative scientists will meet in January to get ready for the upcoming field season. Becoming prepared for this upcoming meeting will dominate Cole and Fischer’s effort on this project for the first quarter. These activities include: testing some laboratory separation methods; becoming familiar with key isotope mixing models, and getting fully up to date on the latest literature in this field.
Jobs Summary: No jobs created. The principal investigator is working 1 mo/year managing and collecting data for this research project. 10% of a Research Specialist currently working at the Institute will be working on this project. (Total jobs reported: 2)
Project Status: Not Started
This award's data was last updated on Jul. 14, 2009. Help expand these official descriptions using the wiki below.