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 hot spots for organic matter mineralization. In this study, we for the first time quantified the total benthic O ₂ 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, that is, the Mariana Trench (2.0 × 10 ² μmol O ₂ m ⁻² d ⁻¹, 10,853 m), the Mussau Trench (2.7 ± 0.1 × 10 ² μmol O ₂ m ⁻² d ⁻¹, 7,011 m), and the New Britain Trench (6.0 ± 0.1 × 10 ² μmol O ₂ m ⁻² d ⁻¹, 8,225 m). Combined with the analyses of total organic carbon and δ ¹³C of total organic carbon in the sediments and previously published in situ O ₂ microprofiles from hadal settings, we suggest that hadal benthic carbon mineralization partly is governed by the surface production and 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.