Sources, Composition, and Export of Particulate Organic Matter Across British Estuaries

E. elena García‐martín, Richard Sanders, Chris d. Evans, Vassilis Kitidis, Dan j. Lapworth, Bryan m. Spears, Andy Tye, Jennifer l. Williamson, Chris Balfour, Mike Best, Michael Bowes, Sarah Breimann, Ian j. Brown, Annette Burden, Nathan Callaghan, Nancy b. Dise, Gareth Farr, Stacey l. Felgate, James Fishwick, Mike FraserStuart Gibb, Pete j. Gilbert, Nina Godsell, Africa p. Gomez‐castillo, Geoff Hargreaves, Carolyn Harris, Oban Jones, Paul Kennedy, Anna Lichtschlag, Adrian p. Martin, Rebecca May, Edward Mawji, Ian Mounteney, Philip d. Nightingale, Justyna p. Olszewska, Stuart c. Painter, Christopher r. Pearce, M. glória Pereira, Kate Peel, Amy Pickard, John a. Stephens, Mark Stinchcombe, Barry Thornton, E. malcolm s. Woodward, Deborah Yarrow, Daniel j. Mayor

Research output: Contribution to journalArticlepeer-review


Estuaries receive and process a large amount of particulate organic carbon (POC) prior to its export into coastal waters. Studying the origin of this POC is key to understanding the fate of POC and the role of estuaries in the global carbon cycle. Here, we evaluated the concentrations of POC, as well as particulate organic nitrogen (PON), and used stable carbon and nitrogen isotopes to assess their sources across 13 contrasting British estuaries during five different sampling campaigns over 1 year. We found a high variability in POC and PON concentrations across the salinity gradient, reflecting inputs, and losses of organic material within the estuaries. Catchment land cover appeared to influence the contribution of POC to the total organic carbon flux from the estuary to coastal waters, with POC contributions >36% in estuaries draining catchments with a high percentage of urban/suburban land, and <11% in estuaries draining catchments with a high peatland cover. There was no seasonal pattern in the isotopic composition of POC and PON, suggesting similar sources for each estuary over time. Carbon isotopic ratios were depleted (−26.7 ± 0.42‰, average ± sd) at the lowest salinity waters, indicating mainly terrigenous POC (TPOC). Applying a two-source mixing model, we observed high variability in the contribution of TPOC at the highest salinity waters between estuaries, with a median value of 57%. Our results indicate a large transport of terrigenous organic carbon into coastal waters, where it may be buried, remineralized, or transported offshore.
Original languageEnglish
Article numbere2023JG007420
JournalJournal of Geophysical Research: Biogeosciences
Issue number4
Publication statusPublished - 6 Apr 2023


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