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

Abstract

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 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, that is, 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 and δ13C of total organic carbon 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 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.

Hadal water biogeochemistry over the Izu–Ogasawara Trench observed with a full-depth CTD-CMS

“…An explanation for a vertical layer ∼ 2000 m in thickness exhibiting anomalously high CH 4 (this study) and 222 Rn (Gamo and Shitashima, 2018) requires sedimentary compounds to be released not only from the axis bottom but also from the trench slopes. Re-suspensions from the trench slope have been commonly suggested by sediment observations that identified the rapid accumulation of the axis sediment, in association with frequent sediment transports from slopes (Nozaki and Ohta, 1993;Glud et al, 2013;Oguri et al, 2013;Luo et al, 2018). As earthquake-induced turbid seawater was indeed evident over the trench slope after earthquake events (Gamo et al, 2007;Kawagucci et al, 2012), this geological force is probably an episodic driver for re-suspension in the IOT.…”

Penetration of Bomb 14C Into the Deepest Ocean Trench

“…Endemic amphipods were collected from the MT (11°N, 142°E), Mussau Trench (MST, 1°N, 149°E), and New Britain Trench (NBT, 6°S, 152–154°E) in early 2017 (Figure and Table ). All three trenches are located in the tropical West Pacific, and the maximum depths of MT (the deepest ocean trench), MST, and NBT are ~11,000, ~7,200, and 9,200 m, respectively (Luo et al, ). Amphipod samples in MT were collected using baited traps during cruise TS‐03 conducted by the Chinese Academy of Sciences in the spring of 2017.…”

Bulk and Active Sediment Prokaryotic Communities in the Mariana and Mussau Trenches

“…However, the hadal zone is not a “biological desert.” Multiple sources of organic matter inputs, combined with special topography and frequent tectonic activities, promote the accumulation of organic matter in the trenches ( Ichino et al, 2015 ; Jamieson, 2015 ; Liu et al, 2018b ). High content of organic matter, abundant microbial cells, and active microbial carbon turnover have been reported in the sediment of multiple trenches, making the hadal trenches “hot spots” of organic carbon degradation in the deep ocean ( Danovaro et al, 2003 ; Glud et al, 2013 ; Wenzhöfer et al, 2016 ; Luo et al, 2018 ).…”