Biogeochemistry of Soils, Sediments, and Surface Waters Across the Upland-to-Wetland Gradient of Coastal Interfaces: Results from the EXCHANGE Consortium


Allison N. Myers-Pigg1,2* (, Stephanie C. Pennington3, Khadijah K. Homolka1, Allison M. Lewis4, Opal Otenburg1, Kaizad F. Patel5, Peter Regier1, Madison Bowe1, Maxim I. Boyanov9, Nathan Conroy7, Donnie J. Day2, Julia McElhinny1, Cooper G. Norris5, Edward J. O’Loughlin6, Jesse Alan Roebuck Jr.1, Lucie Stetten6, Kenneth M. Kemner6, Nicholas D. Ward1,8, Vanessa Bailey5


1Marine and Coastal Research Laboratory, Pacific Northwest National Laboratory, Sequim, WA; 2The University of Toledo, Toledo, OH; 3Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, MD; 4Lawrence Berkeley National Laboratory, Berkeley, CA; 5Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA; 6Argonne National Laboratory, Lemont, IL; 7Los Alamos National Laboratory, Los Alamos, NM; 8 Department of Oceanography, The University of Washington–Seattle, WA; 9Institute of Chemical Engineering, Bulgarian Academy of Sciences, Sophia, Bulgaria



Coastal terrestrial-aquatic interfaces (TAIs) are hydrologically and biogeochemically dynamic, creating functional gradients that vary substantially over space and time. Cohesive datasets across geographically distributed sites enable an understanding of coastal ecosystem biogeochemical control points and support the transferability of new process knowledge. To achieve a broad and coordinated sampling effort, researchers convened the EXploration of Coastal Hydrobiogeochemistry Across a Network of Gradients and Experiments (EXCHANGE) consortium, as part of the Coastal Observations, Mechanisms, and Predictions Across Systems and Scales–Field, Measurements, and Experiments project.

This consortium is a network of researchers that collaborate on the design, methodology, and collection of samples from TAIs in the Great Lakes and Mid-Atlantic regions (Chesapeake and Delaware Bays) of the continental United States. In the Fall of 2021, the EXCHANGE Consortium collected samples from 52 coastal TAIs spanning upland, transition, and wetland soils as well as adjacent surface waters to assess the baseline spatial heterogeneity in chemical forms and distribution of carbon (C), nutrients, and redox-sensitive elements. Researchers found significant differences in physicochemical properties across the coastal TAI regardless of region, while variability in water quality and nutrient concentrations in the surface waters were regionally dependent. The data shows that while the concentrations of water-exe organic C were not statistically different, the optical properties of extracted dissolved organic matter (DOM) varied between upland to wetland sample locations, irrespective of region. The corresponding DOM composition in nearby surface waters was distinct from that of soil-extracted DOM from all gradient locations. Oxygen consumption and greenhouse gas concentration patterns during short-term seawater inundation experiments are explained by local soil physical and chemical properties and landscape-scale gradients in salinity exposure. The preliminary results suggest that the region (Great Lakes or Mid-Atlantic) is most important for understanding heterogeneity in surface water biogeochemical parameters, while the position across the upland-to-wetland gradient largely characterizes the variability in soil biogeochemistry. These results are important to validate the range in input parameters of biogeochemical models at transect and regional scales, aiding in the predictive understanding of coastal biogeochemical function.