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Ecological importance of organic carbon, nitrogen, and phosphorus in watersheds affected by land use and climate change
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Carbon, nitrogen and phosphorus are elements necessary to the creation and persistence of life. Previous work shows that organic forms of C, N, and P can comprise a substantial proportion of the total N and P in surface waters (Kaushal and Lewis 2003, Kaushal and Lewis 2005, Pellerin et al. 2006). Yet, the cycling of organic N and P has been poorly incorporated into existing paradigms of nutrient cycling due to a lack of knowledge regarding generation and metabolism. Our work at the Baltimore Ecosystem Study LTER shows that biologically reactive forms of organic C, N, and P can be generated in great quantity across gradients of land use in the Chesapeake Bay watershed. It also shows that changes in climate can influence the amount, form, and stoichiometry of C, N, and P exported from human land uses with important implications for coastal waters (Kaushal et al. Submitted, Kaushal et al. In prep). Although not typically quantified, organic forms of carbon, nitrogen, and phosphorus may be an important supply of nutrients contributing to eutrophication, and changes in the abundance of inorganic vs. organic nutrients can be an important predictor of microbial community structure and function (Findlay and Sinsabaugh 2006, Kaushal et al. In preparation). More information is available at http://www.kaushallab.cbl.umces.edu/
Figure 1. Preparative scale column chromatography to isolate chemical fractions of dissolved organic matter for chemical and isotopic analyses. Photo: Sujay Kaushal
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Figure 2. Leucine incorporation and epifluorescent microcoscopy to determine bacterial production of microbes on different organic matter sources. Photo: Unknown
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Figure 3. Short-term incubations to measure uptake of inorganic and organic nutrients in streams during ambient temperatures. Photo: Sujay Kaushal
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References
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Findlay, S., R.L. Sinsabaugh. 2006. Large-scale variation in subsurface stream biofilms: a cross-regional comparison of metabolic function and community similarity. Microbial Ecology 52: 491-500.
Kaushal, S.S. and W.M. Lewis, Jr. 2003. Patterns in the chemical fractionation of organic nitrogen in Rocky Mountain streams. Ecosystems 6: 483-492.
Kaushal, S.S. and W.M. Lewis, Jr. 2005. Fate and transport of dissolved organic nitrogen in minimally disturbed streams of the Colorado Rockies. Biogeochemistry 74: 303-321.
Pellerin, B., S.S. Kaushal, and W.H. McDowell. 2006. Does anthropogenic nitrogen enrichment increase organic nitrogen concentrations in runoff from forested and human-dominated watersheds? Ecosystems 9: 852-864.
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