Terrestrial dissolved organic matter distribution in the North Sea

Painter, Stuart C.; Lapworth, Dan J. ORCID: https://orcid.org/0000-0001-7838-7960; Woodward, E. Malcolm S.; Kroeger, Silke; Evans, Chris D. ORCID: https://orcid.org/0000-0002-7052-354X; Mayor, Daniel J. ORCID: https://orcid.org/0000-0002-1295-0041; Sanders, Richard J. ORCID: https://orcid.org/0000-0002-6884-7131. 2018 Terrestrial dissolved organic matter distribution in the North Sea. Science of the Total Environment, 630. 630-647. https://doi.org/10.1016/j.scitotenv.2018.02.237

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Abstract/Summary

The flow of terrestrial carbon to rivers and inland waters is a major term in the global carbon cycle. The organic fraction of this flux may be buried, remineralized or ultimately stored in the deep ocean. The latter can only occur if terrestrial organic carbon can pass through the coastal and estuarine filter, a process of unknown efficiency. Here, data are presented on the spatial distribution of terrestrial fluorescent and chromophoric dissolved organic matter (FDOM and CDOM, respectively) throughout the North Sea, which receives organic matter from multiple distinct sources. We use FDOM and CDOM as proxies for terrestrial dissolved organic matter (tDOM) to test the hypothesis that tDOM is quantitatively transferred through the North Sea to the open North Atlantic Ocean. Excitation emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) revealed a single terrestrial humic-like class of compounds whose distribution was restricted to the coastal margins and, via an inverse salinity relationship, to major riverine inputs. Two distinct sources of fluorescent humic-like material were observed associated with the combined outflows of the Rhine, Weser and Elbe rivers in the south-eastern North Sea and the Baltic Sea outflow to the eastern central North Sea. The flux of tDOM from the North Sea to the Atlantic Ocean appears insignificant, although tDOM export may occur through Norwegian coastal waters unsampled in our study. Our analysis suggests that the bulk of tDOM exported from the Northwest European and Scandinavian landmasses is buried or remineralized internally, with potential losses to the atmosphere. This interpretation implies that the residence time in estuarine and coastal systems exerts an important control over the fate of tDOM and needs to be considered when evaluating the role of terrestrial carbon losses in the global carbon cycle.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.scitotenv.2018.02.237
UKCEH and CEH Sections/Science Areas:	Soils and Land Use (Science Area 2017-)
ISSN:	0048-9697
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	absorption, fluorescent dissolved organic matter (FDOM), chromophoric dissolved organic matter (CDOM), dissolved organic carbon (DOC), excitation-emission matrix parallel factor analysis (EEM-PARAFAC), North Sea, biogeochemistry
NORA Subject Terms:	Marine Sciences
Date made live:	28 Feb 2018 14:40 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/519236

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