Current Research
Recovery of biogeochemical function in degraded urban stream ecosystems?
With funding from the National Science Foundation, the NC Water Resources Research Institute and the NC Department of Natural Resources we are examining how watershed urbanization affects the structure and function of receiving streams. The central goal of the project is to to examine how urban bigoeochemical signals are transported and transformed through river networks and the extent to which stream restoration and preservation actions can dampen urban impacts on downstream ecosystems. Subprojects include examining how urbanization alters patterns of stream metabolism (PhD student Elizabeth Sudduth), comparing the structure and function of denitrifying microbial communities between urban and forested streams (Duke PhD student Jenny Wang (Wright lab)), examining how urbanization and restoration affect stream macrobenthos communities (UNC PhD student Christy Violin), developing structural equation models linking urban influences (stormwater, sewerage, impervious surfaces) with stream water quality, sediment pollutants and microbial community structure and function (with Dean Urban and PhD student Kayleigh Somers).
The Biogeochemical Consequences of Converting Farm Fields to Wetlands
With funding from the Department of Energy's National Insitute of Climate Change Research, the Great Dismal Swamp Mitigation Bank, LLC, the NC Water Resources Research Institute and the NC Department of Environment and Natural Resources we are examining changes in water quality and trace gas emissions resulting from NC's largest wetlands mitigation project. Our work examines solute and gaseous fluxes from a 400ha former agricultural field that was converted to a wetland in 2006. Our goal is to understand the consequences of converting formerly cultivated and fertilized farmland to wetland with respect to promoting denitrification vs. generating dissolved phosphorus and greenhouse gas pollutants. Postdoctoral associate Marcelo Ardon is focused on understanding controls over solute losses while PhD student Jen Morse is focused on understanding trace gas emissions from the site. This work is in collaboration with Martin Doyle (UNC) and Geoff Poole (Montana State University). A project overview is available here
Rhizosphere Priming Effects on Soil N Availability
With funding from the USDA NRI program and the Department of Energy we are working in conjunction with the Duke Forest Free Air CO2 enrichment experiment. Our research effort examines the extent to which trees can increase their carbon allocation to root growth and soluble root exudates under elevated atmospheric CO2 and the role that root exudates may play in altering belowground nitrogen cycling in the rhizosphere (or near root zone). This work is currently spearheaded by former postdoctoral assocate Rich Phillips (now a faculty member at IU). Andrea Martin runs the field and lab effort here at Duke.
Environmental Impacts of Nanomaterials
As part of the recently funded (EPA & NSF) Center for the Environmental Implications of Nanotechnology (CEINT), we are examining the effects of manufactured nanomaterials on microbial community structure and function in soils and sediments. This project began in October 2008 and our initial work is focused on understanding how silver nanoparticles (often produced for their antimicrobial properties) affect microbes in complex media. Postdoctoral associate Ben Colman and visiting research fellow Dr. Liyan Yin are leading this effort.
Dissolved organic nitrogen cycling in forested streams
With no current major funding but a great deal of enthusiasm we are working to understand the role of dissolved organic nitrogen in carbon and nitrogen cycling in forested streams. Bernhardt and PhD student Brian Lutz are working collaboratively with Pat Mulholland (Oak Ridge National Lab) and Brian Roberts (LUMCON) to understand what controls the variation in DON concentrations, bioavailability and composition across southern Appalachian forested watersheds.
The Salmonid Rivers Observatory Network (SaRON): Relating Habitat Quantity and Quality to Salmon Productivity for Pacific Rim Rivers
In collaboration with Jack Stanford at the Flathead Lake Biological Station we are actively involved in a large-scale effort to understand the links between large rivers and their floodplains. The overarching goal of the SARON project (funded by the Gordon and Betty Moore Foundation) is to develop a holistic understanding of controls on salmon population dynamics in the major rivers of the Pacific Rim. Within this large project Bernhardt and PhD student Alison Appling are collaborating with Geoff Poole (Montana State) and John Kimball (FLBS) to develop a fluvial ecosystem model that links a dynamic hydrologic model (WREN-NEO) with aboveground vegetation dynamics and a microbial biogeochemical process model.