Identifying dynamic sources and transformations of dissolved organic matter in coastal watersheds exposed to extreme flooding
EMSL Project ID
51347
Abstract
The primary objective of this proposal is to improve mechanistic understanding of the hydrobiogeochemical processes governing the cycling of organic matter (OM) across the land-to-sea continuum associated with hot moments of oxygenation and GHG production. Specifically, we request EMSL resources for OM structural characterization, allowing us to evaluate the impact of subsurface oxygenation during seawater inundation events and the underlying mechanisms behind observed CH4 and CO2 fluxes during flood events and in surface waters along a study domain spanning from the headwaters to the coastal terrestrial-aquatic interface of a small first-order watershed in the Pacific Northwest--Beaver Creek. The potential utility of 1-D and 2-D NMR techniques, coupled with LC/MS metabolomics approaches to understand environmental chemistry is enormous, yet this remains an underutilized tool in environmental research. Thus, we propose to apply these techniques to understudied OM compositional shifts during potential 'hot-moments' of biogeochemical cycling. This work will support the DOE-BER mission to develop process-rich understanding of hydrological and biogeochemical cycles in watersheds by developing a mechanistic understanding of a poorly constrained aspect of the Earth system--the dynamic processing and/or storage of OM at the coastal interface. The mechanisms driving transport and transformation of OM and ecosystem responses to perturbations will be evaluated on molecular to ecosystem scales in the context of biogeochemical process-model needs, leverage past and present DOE investments, and address knowledge gaps identified in recent DOE workshop reports. We will address several of the possible molecular underpinnings associated with GHG emissions in coastal environments in the context of OM substrate character and quantity: 1) The influence of two-way hydrologic exchange driven by tidal cycles on above and belowground DOM structure, composition and abundance; 2) The role of extreme flood events on alterations of dissolved OM (DOM) composition in relation to oxygen dynamics and GHG production in the subsurface; and 3) Molecularly-selective decomposition, mobilization, and stabilization of DOM during riverine transport from watershed headwaters to the sea. Our overarching hypothesis is that GHG production will be linked to structural alterations to and composition of DOM along the land-to-sea continuum, which will be hydrologically driven and modulated by abiotic and biotic transformations related to specific environmental conditions (e.g., oxygen availability).
Project Details
Project type
Large-Scale EMSL Research
Start Date
2020-10-01
End Date
2022-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members