Benthic Carbon Mineralization in Hadal Trenches: Insights From In Situ Determination of Benthic Oxygen Consumption

Hadal trenches have been proposed as depocenters of organic material and hotspots for organic matter mineralization. In this study, we for the first time quantified the total benthic O2 uptake in hadal trenches using in-situ chamber incubations. Three trenches in the tropical Pacific were targeted and exhibited relatively high diagenetic activity given the great water depths, i.e., the Mariana Trench (2.0×102 μmol O2 m-2 d-1, 10,853 m), the Mussau Trench (2.7±0.1×102 μmol O2 m-2 d-1, 7,011 m), and the New Britain Trench (6.0±0.1×102 μmol O2 m-2 d-1, 8,225 m). Combined with the analyses of total organic carbon (TOC) and δ13C of TOC in the sediments and previously published in-situ O2 microprofiles from hadal settings, we suggest that hadal benthic carbon mineralization partly is governed by the surface production but also is linked to the distance from land. Therefore, we highlight that terrestrial organic matter can be of importance in sustaining benthic communities in some hadal settings.