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Carbon Cycle & Ecosystems

Dissolved organic carbon (DOC) is an important water quality parameter because of its central role in many aquatic ecosystem processes. Both the amount and quality of DOC are significant factors, yet field measurements are relatively sparse, in particular for quality. Remote sensing can potentially provide much wider coverage, but can gather information only from the colored portion of the DOC pool (i.e. CDOM, colored dissolved organic matter). Extending CDOM measurements to bulk DOC concentration requires knowledge of CDOM:DOC ratios, but these have considerable variability that is poorly understood. In coastal waters, some of this variability is driven by CDOM:DOC of the terrestrial end member, which is the outcome of both terrestrial and aquatic processes within basins. Understanding variability of CDOM:DOC within and across basins over time requires teasing apart the terrestrial and aquatic factors affecting the ratio. In this proposal, our objective is to: Quantify DOC quantity and quality (as the absorption coefficient (α) and other related measures of CDOM) across season and flow conditions along the aquatic continuum from headwater streams to large rivers to the coastal zone by linking terrestrial and aquatic remote sensing information, models, and field measurements. To achieve this objective, we will 1) develop a remote sensing based approach for predicting DOC and CDOM inputs from terrestrial to freshwater aquatic systems applicable at regional scales. A regional sampling program will be initiated in conjunction with ongoing monitoring efforts to ensure sufficient data to develop empirically based models of inputs as a function of terrestrial ecosystem state; 2) develop and apply a DOC/CDOM process model within an existing river network modeling environment to predict how CDOM:DOC ratios change as a function of mixing, dilution, aquatic production, photorespiration, and microbial respiration within the river system; 3) test whether model predictions of CDOM correspond with remotely sensed estimates of ag412 in coastal environments. Our study domain will be the coastal zone along the U.S. Atlantic Seaboard and Gulf of Mexico and its contributing drainage basin. This study area is targeted because it provides a range of climate, land use, drainage basin areas and elevation that will be necessary to assess the general applicability of the model. We will initially target several drainage basins that have sufficient downstream field measurements of CDOM and DOC to test/calibrate the model. Expected Significance: Society is faced with fundamental concerns regarding the quality of drinking water and the response of the global carbon cycle to ongoing anthropogenic perturbation of atmospheric CO2. Our objective informs both of these concerns by developing the tools, based on remote sensing information, that will 1) constrain regional estimates of the fate of terrestrial carbon by accounting for fluvial exports, 2) account for the role of freshwater aquatic systems in watershed carbon cycling, 3) provide estimates of carbon inputs and their quality to coastal systems to better constrain carbon fluxes and fate in marine environments, and 4) map throughout river systems DOC and CDOM concentrations that are relevant to drinking water supplies and flux of pollutants associated with organic carbon molecules. A regional perspective is necessary in order to develop remote sensing approaches for broader application. Our work will inform the planning of the next generation of remote sensing instrument under development (e.g. GEO-CAPE), as well as determine the density and distribution of in situ measurements in emerging national sampling networks.

Project PI: Wilfred Wollheim/University of New Hampshire

Co-Director, Water Systems Analysis Group Institute for the Study of Earth, Oceans and Space University of New Hampshire, Durham NH, 03824

Phone: (603) 862-0812

Email: Wil.Wollheim@unh.edu

http://www.wsag.unh.edu/Wollheim/wollheim.html

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Started: Aug 10, 2010

Last Activity: Dec 16, 2010

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