PIs: Louis A. Kaplan, Anthony K. Aufdenkampe, J. Denis Newbold, Robert H. Findlay, and Peggy H. Ostrom
Naturally occurring organic molecules dissolved in water constitute the largest pool of organic matter in aquatic ecosystems. Within streams and rivers, molecules that originate in terrestrial vegetation and are modified within soils and groundwater by microorganisms during movement to the channel, are the dominant source of organic matter. These terrestrially derived molecules in transport downstream contribute to the biologically useful chemical energy present in freshwater and coastal marine environments. Our research uses a novel application of stable isotopes to quantify those contributions throughout a drainage network, and we frame our investigations within the context of scaling rules that facilitate the transfer of information from one habitat or system to others. We will grow young deciduous trees in an atmosphere enriched with the stable isotope of carbon, harvest and compost the trees, and extract the compost to prepare a leachate of complex, microbially modified molecules, and follow the fate of those organic molecules in systems which range from small laboratory reactors to a 5th order stream. Combining scaling rules derived from the knowledge of how streams "grow" as they flow towards the ocean with scaling rules associated with nutrient uptake in streams, allows us to test hypotheses concerning how organic molecules are used for energy within a stream network.
This research has broad implications for the use of scaling rules in ecological studies and for the drinking water industry where organic molecules provide both nutrients for the unwanted growth of microorganisms in distribution systems and the building blocks for the carcinogenic byproducts of disinfection. Our approach also may provide a predictive tool that can be used to learn about the fate and transport of anthropogenic contaminants that are transported downstream through their association with naturally occurring organic molecules.
