Climate Change and Dissolved Organic Carbon Fluxes
Response surface showing modeled DOC flux and concentration as a function of discharge and month for the Penobscot River at Eddington, Maine.
The purpose of this project is to investigate the links between terrestrial, estuarine, and marine carbon cycling and fluvial transport of freshwater, nutrients, and dissolved organic carbon (DOC) to the near-coastal ocean. The project analyzes fluvial carbon export that integrates complex interacting processes occurring in natural and human-impacted terrestrial and aquatic environments. Changes in fluvial carbon export may indicate changes in carbon cycling in terrestrial ecosystems that are difficult to quantify directly but that may affect exchanges between the biosphere, geosphere, and atmosphere. Detecting changes in carbon export can provide insight into ongoing changes in terrestrial carbon cycling. In northern temperate forested ecosystems increases or decreases in carbon export may reflect a shift from carbon sink to carbon source or vice versa. Changes in carbon export can influence aquatic and marine biogeochemical processes including eutrophication, hypoxia, carbon sequestration or release from soils, sediments and biomass, ocean net primary productivity. This project examines the controls on the fluvial export of terrestrially-derived DOC including seasonal concentration-discharge relations, climatic variability, abundance of wetlands, types of wetlands, forest composition and other landscape variables. Historic hydrologic variability is studied to understand how climate change is affecting carbon cycling and carbon export.
Why is this research important?
The evidence suggests that the global hydrologic cycle is intensifying. In the northeastern U.S. this hydrologic response to climate change includes an increase in precipitation and runoff and is projected to result in substantial changes in the seasonal delivery of water and organic carbon to the near-coastal ocean, and to an increase in summer drought severity. These hydrologic changes are altering the timing and magnitude of the delivery of dissolved organic carbon to the near-coastal ocean in the Gulf of Maine. Evidence suggests that increasing discharge is affecting nutrient inputs to the Gulf of Maine and that increasing export of DOC may be reducing light absorption by phytoplankton reducing primary productivity that could ultimately affect fisheries in the region. Changes in climate and hydrologic conditions may also affect the abundance, type, and connectivity of wetlands that, in turn, will affect the export of organic carbon.
