Streams are important in the cycling of carbon. Almost half of the carbon in watersheds enter streams and rivers where it is converted to a carbon gas or transported downstream. Understanding of these processes come largely from studying continually flowing streams and rivers. Nearly 60% of streams in the United States are intermittent or ephemeral, and all stream and river networks have intermittent streamflow in their contributing networks. Yet little is known about the role that these periodically dry streams play in the processing and movement of carbon through the stream network. This award will address the question of how and when do spatial and temporal patterns of intermittence affect carbon concentrations and characteristics. The researchers will explore flow intermittence effects on dissolved organic carbon and the relative influence of legacy effects of drying during conditions when instream processes control dissolved organic carbon (e.g., growing season) and via connectivity to terrestrial sources during conditions when dissolved organic carbon is typically controlled by flow (e.g., high flows). The broader impacts include training of students, working with local watershed managers, coordinating with research networks, and producing a museum exhibit.
Network scale approaches to understanding stream carbon cycling often make assumptions that are not appropriate for intermittent networks (e.g., homogeneous instream processing rates), and continental and global assessments of stream carbon cycling ignore the role of these streams, potentially missing a major component of the global carbon cycle. This award will transform approaches to thinking about streamflow intermittence and its effects on carbon cycling and transport by integrating network thinking and intermittency effects on biogeochemistry. This award will develop the conceptual and empirical basis for understanding when, where, and how streamflow intermittence affects instream process rates, connectivity to upstream carbon sources, and carbon concentrations and export. The research has two specific aims: Aim 1: Assess spatial and temporal effects of streamflow intermittence on spatial patterns of dissolved organic carbon. This will be accomplished through combining spatially extensive continuous flow presence/absence monitoring with detailed synoptic characterization of dissolved organic carbon concentrations and characteristics across an intermittent stream network. Aim 2: Assess how and when intermittence affects instream process rates and instream process controls on dissolved organic carbon concentrations. The researchers will use high-frequency monitoring of streamflow, dissolved organic carbon concentrations, and instream metabolism. The research will lay the groundwork for integrating heterogeneity into network models of stream carbon cycling.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
