EAR-PF: Linking lakes to the landscape: mechanisms that control terrestrial subsidies to pelagic food webs

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Dr. Steven Sadro has been awarded an NSF Earth Sciences Postdoctoral Fellowship to implement a research and education program at the University of California, Riverside. He will use comparative and experimental approaches to investigate the extent to which variability in the concentration and composition of terrigenous inputs to lakes affects the transfer of terrestrial carbon into pelagic food webs. Terrestrial ecosystems export a considerable amount of organic matter into lakes, but the degree to which such material supports pelagic food webs is debated, and the environmental controls of such subsidies are poorly understood. In this study, the natural abundance of carbon (13C and ∆14C), nitrogen (15N), and hydrogen (2H) isotopes will be used to determine terrestrial contributions to aquatic food webs. Seasonal and spatial driven variation in the quantity and quality of terrestrial inputs will be used along with experimental manipulations to illustrate mechanisms of control on carbon transfers to pelagic organisms. These studies will be carried out in high-elevation lakes, which have consistent spatiotemporal patterns in dissolved organic matter composition driven by elevation and snowmelt dynamics, making them ideal natural laboratories for ecosystem studies of carbon flow. Lakes are natural repositories of terrestrial organic matter. The extent to which this material is decomposed, stored, or biologically cycled within lakes has important implications for energy flow, food web structure, and ultimately, the amount of carbon that is exported or released back into the atmosphere as carbon dioxide. However, evidence that terrestrial carbon is incorporated into aquatic food webs remains controversial. By characterizing the mechanisms that control the flow of terrestrial carbon in aquatic food webs, this research will illustrate linkages between organisms and help refine food web models for aquatic systems. Furthermore, high-elevation ecosystems are sensitive to the effects of climate warming; understanding carbon cycling in these systems, in particular, is a critical first step in predicting how ongoing changes in soil, vegetation, and hydrological dynamics will affect aquatic ecosystems. Dr. Sadro will directly incorporate undergraduates in both field and laboratory aspects of this research. He will assist in developing and leading a university field aquatic ecosystem science course taught at the Sierra Nevada Aquatic Research Laboratory facilities, a UC Reserve located in the eastern Sierra. Dr. Sadro will also contribute to the development of a watershed education curriculum serving under-represented secondary school students within the western Sierra Nevada Woodlake Union High School near Visalia, California.