High carbon mineralization rates in subseafloor hadal sediments - Result of frequent mass wasting

Abstract

Only recently it has been realized that hadal trenches harbor a surprisingly high biological activity (Bartlett, 2009;Danovaro et al., 2003;Jamieson, 2015). In situ measurements have documented that microbial oxygen depletion at the seafloor surface in deep sea trenches is far more efficient than would be expected at such great water depths (Glud et al., 2013;Luo et al., 2018;Wenzhöfer et al., 2016). These findings suggest that the input of degradable material must be considerably greater than estimated assuming purely vertical transport from the euphotic zone either driven by hydrographic and/or down slope funneling of material or by mass wasting (

Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

“…These assessments demonstrate that despite highly elevated microbial mineralization, hadal regions accumulate relatively large amounts of organic material. The current findings align with other recent investigations that demonstrating the importance of tectonic induced mass wasting for translocating organic carbon to the hadal environment (Bao et al., 2018; Kioka et al., 2019b; Zabel et al., 2022) and previous indirect evidence arguing for high carbon accumulation in hadal sediments (Luo et al., 2017; Xu et al., 2021), as well as recent findings of highly elevated sequestration of black carbon in some hadal settings (Zhang et al., 2022).…”

“…Additionally, our assessments also suggest that trenches are characterized by continuous accumulation of material focusing, even during periods without mass wasting (Figure 4b). Both the continuous and the erratic enhancement of material deposition might have important implications for the balance between microbial mineralization and burial of organic material and thereby long‐term carbon sequestration in trench regions and the deep sea in general (Zabel et al., 2022).…”

“…Generally, the vertical transport of organic material from the surface ocean attenuates strongly with ocean depth (Berger et al., 1987), but during the past two decades it has been realized that hadal trenches can act as depocenters for organic material (Danovaro et al., 2003; Ichino et al., 2015; Xu et al., 2021). In addition, some trench sediments hold surprisingly high levels of microbial and meiofaunal biomass (e.g., Brandt et al., 2020; Itoh et al., 2011; Schauberger et al., 2021; Zabel et al., 2022) and hadal sediments appear to express elevated O 2 consumption rates as compared to adjacent abyssal sites with water depths of 5,000–6,000 m (Glud et al., 2013, 2021; Luo et al., 2019; Wenzhöfer et al., 2016). These observations imply that deposited organic materials in trenches do not only consist of resilient pre‐aged organic material but also include relatively labile and nutritious organics that can sustain highly active microbial communities thriving at extreme hydrostatic pressure.…”

Caracterización de la Materia Orgánica Particulada de la Fosa de Atacama Mediante Lípidos Polares Intactos e Isótopos Estables.

“…This result is consistent with previous studies in the Japan and Atacama Trenches (Nakatsuka et al, 1997;. However, deeply buried sediment from the Atacama Trench has revealed phases of slow pelagic sedimentation in the past that alternate with rapid mass-wasting events, which fuel microbial carbon turnover at remarkably high rates Zabel et al, 2022). Thus, we expect that the recycling by piezophilic bacteria in the hadal region of organic matter originated from primary production in the surface ocean and the downslope transport will alter the isotopic composition of sedimentary carbon and nitrogen (Xu et al, 2018 and references therein).…”

“…However, high remineralization due to intense heterotrophic activity has also been demonstrated in the Atacama Trench , Glud et al, 2021. Therefore, although previous studies have suggested an important contribution of OM from material accumulated in sediments on the continental shelf, to hadal benthic zone (Flores et al, 2022;Oguri et al, 2022;Zabel et al, 2022), the contribution of OM from the euphotic zone to hadalpelagic zone could be more than expected.…”