Organic carbon, in the form of dissolved molecules transported in stream water, is processed for energy by microorganisms that live on the streambed. That processing constitutes a critical link in the global carbon cycle. The sources of much of the stream carbon are the upper layer of soils within small watersheds and algae that live in streams. Looking out over a drainage network, the investigators will explore how the quality of the organic molecules changes with distance downstream and how those changes influence the composition of the communities of streambed microbes using that food resource. To characterize the thousands of individual organic molecules dissolved in stream water and the vast diversity of microorganisms living in streams, the research team will exploit novel methods that link the new frontiers in molecular microbiology and analytical organic geochemistry. This proposal will be carried out in waters that range in size from small streams to small rivers within temperate and tropical forests. The research goals include advancing knowledge of stream ecosystems across drainage networks and forging a broad model of stream ecosystems in the global carbon cycle.
Understanding the global carbon cycle is a critical scientific need of society and recent studies suggest that freshwater streams and rivers play a significant role within it. By better understanding the relationships between stream microorganisms and the organic carbon in freshwater streams, this study will contribute to our overall understanding of a key component of the global carbon cycle. Because microorganisms are invisible to the naked eye, getting students excited about the diversity of microorganisms and organic molecules and the complexity of their ecological interactions is difficult. The research team will develop educational materials that depict the basic concepts in microbiology and organic geochemistry with an emphasis on the vital roles that microorganisms play in aquatic ecosystems. At facilities within each of the study catchments the investigators and their educator colleagues will hold two-day summer teacher workshops to expose secondary school teacher to the microbial world of streams. The workshops will be timed to allow participants to mirror the field and laboratory activities of the scientists. In addition, 1 graduate student, 1 post-doctoral scientist, and 7 undergraduates will receive training during the project.