Earthquake-enhanced dissolved carbon cycles in ultra-deep ocean sediments

Abstract

Hadal trenches are unique geological and ecological systems located along subduction zones. Earthquake-triggered turbidites act as efficient transport pathways of organic carbon (OC), yet remineralization and transformation of OC in these systems are not comprehensively understood. Here we measure concentrations and stable- and radiocarbon isotope signatures of dissolved organic and inorganic carbon (DOC, DIC) in the subsurface sediment interstitial water along the Japan Trench axis collected during the IODP Expedition 386. We find accumulation and aging of DOC and DIC in the subsurface sediments, which we interpret as enhanced production of labile dissolved carbon owing to earthquake-triggered turbidites, which supports intensive microbial methanogenesis in the trench sediments. The residual dissolved carbon accumulates in deep subsurface sediments and may continue to fuel the deep biosphere. Tectonic events can therefore enhance carbon accumulation and stimulate carbon transformation in plate convergent trench systems, which may accelerate carbon export into the subduction zones.

Tracing Organophosphate Ester Pollutants in Hadal Trenches─Distribution, Possible Origins, and Transport Mechanisms

“…Concurrently, there is an increase in high-molecular-weight recalcitrant compounds, a phenomenon known as “solvent depletion (Figure ). This effect is notably more pronounced in the V-shaped, deep regions of our study area compared to shallower areas like the Arctic . As this material reaches the sediment, it undergoes a “filtering” process (Figure ), which effectively isolates these organic particles from the surrounding seawater and incorporates them into the sediment.…”

Comparative single-cell genomics of Atribacterota JS1 in the Japan Trench hadal sedimentary biosphere

“…The depth of SMTZ at site M0090D was relatively shallower than that of other sites, at around 4.5 mbsf, suggesting relatively high activities of organic matter-fueled sulfate reduction and methanogenesis. The difference in methane profiles among sites may be due to the pervasive existence of earthquake-generated turbidite deposits along the Japan Trench ( 9 , 31 ), which also affect TOC concentration and microbial fermentation in situ ( 10 ).…”

“…Earthquake-related events in the Japan Trench have also been reported to remobilize fine-grained, young TOC-rich sediments over an extensive area of the Japan Trench axes [e.g., the 2011 Tohoku-oki earthquake (Mw 9.1) delivered >1 Tg of C to the Japan Trench] ( 9 ). Earthquake-enhanced dissolved organic and inorganic carbon have also been observed in subseafloor sediments ( 10 ), potentially sustaining the heterotrophic deep sedimentary biosphere.…”

“…Specifically, in organic-rich surface sediments [approximately 30 cm below seafloor (cmbsf)], heterotrophic microorganisms, such as Bacteroidetes, predominates, whereas more oligotrophic trenches, such as the Mariana and Yap Trenches, exhibit archaeal members within Thaumarchaeota ( 11 , 12 ). Notably, Japan Trench sediments display a relatively shallow depth of oxygen penetration and an elevated sulfate-methane transition zone (SMTZ) due to heightened methane flux ( 10 , 13 ). Consequently, anaerobic heterotrophic and methanogenic metabolism plays vital roles in breaking down refractory organic matter in deeper layers ( 14 )…”