Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon

W. R. Hunter*, A. Jamieson, V. A. I. Huvenne, U. Witte

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)
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The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3-7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. C-13 and N-15 labels were traced into faunal biomass and bulk sediments, and the C-13 label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0-1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal-bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

Original languageEnglish
Pages (from-to)67-80
Number of pages14
Issue number1
Publication statusPublished - 8 Jan 2013

Bibliographical note

The authors gratefully acknowledge the help and support of the officers and crew of the RRS James Cookand ROV ISIS, Doug Masson and the scientific team during
cruise JC036. We also acknowledge Margarita Machairopoulou (U. Aberdeen), for her assistance with macrofaunal sorting and identification, and Val Johnston (U. Aberdeen). Darryl Green and Jez Evans (NOC, Southampton) assisted with the shipment of equipment, chemicals and samples. The authors thank David Harris
(UC Davis Stable Isotope Facility), Barry Thornton and Maureen Procee (James Hutton Institute) for their assistance with stable-isotope analysis. This study forms part of the FP7 EU HERMIONE project (Hotspot Ecosystem Research and Man’s Impact on European seas, grant agreement number: 226354). WRH was supported by a NERC Doctoral Training Grant (NE/G523904/1)


  • Benthic food-web
  • last European Deglaciation
  • Armorican margin bay
  • deep-sea sediments
  • carbon flows
  • NE Atlantic
  • Continental-margin
  • bacterial carbon
  • Nazare Canyon
  • Goban Spur


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