PNNL

The Science 

Coastal surface waters contain dissolved organic matter (DOM), which affects water quality and coastal biogeochemistry. DOM chemical composition is known to differ between rivers and estuaries/lacustuaries; however, how those differences are affected by region and ecosystem—are poorly understood. Using a coordinated community research approach, samples solicited from 47 coastal sites in the Mid-Atlantic and Great Lakes regions were analyzed using fluorescence spectroscopy and mass spectrometry. The composition of DOM depended more on water type (river or estuary/lacustuary) than on geography (Mid-Atlantic or Great Lakes), and similar patterns occurred in both marine and freshwater coastal systems.

The Impact 

Using a broad dataset spanning freshwater and saltwater coasts, researchers identified consistent chemical differences in dissolved organic matter between rivers and estuaries. This study revealed coastal patterns that are difficult to capture through traditional research. The work shows generalizable patterns in dissolved organic matter composition may exist in both freshwater and marine coastal zones. These findings enable more transferable and scalable predictions of biogeochemistry in Earth system models and highlight pH as a potentially universal indicator of organic matter transformation. In addition to the technical findings, this study also demonstrates the power of coordinated community science.

Summary 

Dissolved organic matter (DOM) in coastal waters affects water quality and biogeochemistry, yet its transformation between rivers and estuaries is poorly understood and is not well-represented in models. DOM in 47 samples collected from the Mid-Atlantic and Great Lakes as part of the community science EXCHANGE consortium was analyzed. Fluorescence spectroscopy and high-resolution mass spectrometry, revealed how DOM composition varies between small tidal and seiche influenced rivers and nearby estuarine waters, linking these molecular patterns to environmental factors such as pH and salinity.

DOM chemistry depended more on water type than on regional setting. River waters contained higher levels of aromatic molecules derived from land, while estuarine waters were enriched in nitrogen and sulfur containing compounds associated with biological and photochemical processing. Despite major physical and chemical differences between regions, these underlying molecular patterns remained remarkably consistent. These shared trends suggest that the transformation of land derived organic matter follows predictable pathways across diverse coastal types, enabling transferable and scalable approaches for understanding and predicting biogeochemistry at the land-water interface.

Contact 

Daniel Stover, Environmental System Science Program, daniel.stover@science.doe.gov 

Vanessa L. Bailey, COMPASS-FME principal investigator, Pacific Northwest National Laboratory, vanessa.bailey@pnnl.gov

Allison Myers-Pigg, corresponding author, Pacific Northwest National Laboratory, allison.myers-pigg@pnnl.gov

Funding 

This research is supported by Coastal Observations, Mechanisms, and Predictions Across Systems and Scales, Field, Measurements, and Experiments (COMPASS-FME), a multi-institutional project supported by the Department of Energy (DOE), Office of Science, Biological and Environmental Research as part of the Environmental System Science Program. The Pacific Northwest National Laboratory leads this project, operating under contract through Battelle Memorial Institute for the DOE. This work was also supported by the Smithsonian Environmental Research Center and the University of Toledo.

Related Links

https://compass.pnnl.gov/FME/COMPASSFME