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Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems
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  • Kazumasa Oguri,
  • Pere Masqué,
  • Matthias Zabel,
  • Heather A Stewart,
  • Gillian MacKinnon,
  • Ashley A Rowden,
  • Frank Wenzhöfer,
  • Ronnie N Glud
Kazumasa Oguri
Hadal & Nordcee, Department of Biology, University of Southern Denmark

Corresponding Author:ogurik@biology.sdu.dk

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Pere Masqué
School of Natural Sciences, Centre for Marine Ecosystems Research, Edith Cowan University
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Matthias Zabel
Center for Marine Environmental Sciences, University of Bremen
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Heather A Stewart
British Geological Survey
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Gillian MacKinnon
Scottish Universities Environmental Research Centre
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Ashley A Rowden
National Institute of Water & Atmosphere Research (NIWA)
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Frank Wenzhöfer
HGF-MPG Group for Deep Sea Ecology and Technology
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Ronnie N Glud
Hadal & Nordcee, Department of Biology, University of Southern Denmark
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Hadal trenches act as depocenters for organic material, although pathways for hadal material transport and deposition rates are poorly constrained. Here we assess, focusing, deposition and accumulation, of material and organic carbon in four hadal trench systems underlying provinces of different net primary productivity in the surface ocean – from the eutrophic Atacama and Kuril-Kamchatka trenches, and the mesotrophic Kermadec Trench, to the oligotrophic Mariana Trench. The study is based on the distributions of 210Pbex, 137Cs and total organic carbon from recovered sediment cores and by applying previously quantified benthic mineralization rates. Periods of steady deposition and discreet mass-wasting deposits were identified from the profiles and the latter were associated with historic recorded seismic events in the respective regions. During periods without mass wasting, the estimated focusing factors along trench axes were elevated, suggesting continuous downslope focusing of material towards the interior of the trenches. The estimated accumulation rates of organic carbon during these periods exhibited extensive site-specific variability but were generally similar to values encountered at much shallower settings such as continental slopes and margins. Organic carbon deposition and accumulation rates during periods of steady deposition was not mirrored by surface ocean productivity, but appeared confounded by local bathymetry. Seismic driven mass wasting events markedly enhanced the accumulation of sediment and organic carbon by factors from 20 to 400. Thus, hadal trenches are important sites for deposition and sequestration of organic carbon in the deep-sea partly due to intensified downslope focusing of material but mainly due to mass-wasting events.