Geochemistry and mineralogy of the sediments in the New Britain shelf-trench continuum, offshore Papua New Guinea: Insights into sediment provenance and burial in hadal trenches

Lin, Gang; Luo, Min; Chen, Linying; Chen, Yilun; Chen, Duofu

doi:10.1016/j.dsr.2021.103621

“…The variations both within and between individual trenches are considerable, presumably due to local bathymetry, and spatiotemporal dynamics as induced by mass‐wasting events. However, the sources and characteristics of the material reaching the trench axes are still poorly resolved (Lin et al., 2021; Luo et al., 2019; Xu et al., 2021). While the deposited organic material sustains high biological activity (Glud et al., 2021), it apparently also leads to considerable sequestration of organic material along the trench axes.…”

Section: Discussionmentioning

confidence: 99%

Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

Oguri

¹

,

Masqué

²

,

Zabel

³

et al. 2022

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Hadal trenches are considered to act as depocenters for organic material, although pathways for the material transport and deposition rates are poorly constrained. Here we assess focusing, deposition and accumulation of material and organic carbon in four hadal trench systems underlying different surface ocean productivities; the eutrophic Atacama and Kuril-Kamchatka trenches, the mesotrophic Kermadec trench and the oligotrophic Mariana Trench. The study is based on the distributions of naturally occurring 210 Pb ex , 137 Cs and total organic carbon from recovered sediment cores and by applying previously quantified benthic mineralization rates. Periods of steady deposition and discreet mass-wasting deposits were identified from the profiles and the latter were associated with historic recorded seismic events in the respective regions. During periods without mass wasting, the estimated focusing factors along trench axes were elevated, suggesting more or less continuous downslope focusing of material toward the interior of the trenches. The estimated organic carbon deposition rates during these periods exhibited extensive site-specific variability, but were generally similar to values encountered at much shallower settings such as continental slopes and margins. Organic carbon deposition rates during periods of steady deposition were not mirrored by surface ocean productivity, but appeared confounded by local bathymetry. The inclusion of deposition mediated by mass-wasting events enhanced the sediment and organic carbon accumulations for the past ∼150 years by up to a factor of ∼4. Thus, due to intensified downslope material focusing and infrequent mass-wasting events, hadal trenches are important sites for deposition and sequestration of organic carbon in the deep sea.Plain Language Summary Hadal trenches (>6,000 m water depth) occupy ∼1% of the world's ocean floor yet are largely underexplored, but recent studies have shown that these environments are depocenters for organic material and microbial activity is intensified when compared to shallower abyssal plains. However, transport and accumulation of sediment material to these hadal trenches is poorly understood. This study investigates sedimentation and accumulation dynamics of organic carbon in trenches using results of radionuclide analysis (in sediment from the Atacama, Kuril-Kamchatka, Kermadec, and Mariana trenches). The analysis shows that trench sediments consist of discreet layers representing both periods of continuous deposition and sudden mass-wasting events often triggered by historic earthquakes. Down slope focusing of material, intensified the deposition along the trench axes. However, the deposition rates exhibited extensive site-specific variations that were partly related to mass-wasting events which greatly enhanced not only mass accumulation but also organic carbon accumulation at the trench axes. Our results illustrate that mass-wasting events play an important role on supplying organic carbon to hadal communities and suggest that hadal tr...

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“…Liu et al reported a similar trend in Hg levels among sampling sites. This could be due to the rapid movement of land-derived materials via rivers, together with the comparatively short distance from the coastline to both the landward and trench axis sites. , Moreover, in sediment samples from the three trenches, total organic carbon (TOC) levels were found to vary from 0.24 to 1.49%. There was no significant correlation between the ∑ 10 OPE concentrations and TOC levels across these trenches.…”

Section: Resultsmentioning

confidence: 99%

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

Xie,

Zhang,

Chen

et al. 2024

Environ. Sci. Technol.

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Unraveling the mysterious pathways of pollutants to the deepest oceanic realms holds critical importance for assessing the integrity of remote marine ecosystems. This study tracks the transport of pollutants into the depths of the oceans, a key step in protecting the sanctity of these least explored ecosystems. By analyzing hadal trench samples from the Mariana, Mussau, and New Britain trenches, we found the widespread distribution of organophosphate ester (OPE) flame retardants but a complex transport pattern for the OPE in these regions. In the Mariana Trench seawater column, OPE concentrations range between 17.4 and 102 ng L −1 , with peaks at depths of 500 and 4000 m, which may be linked to Equatorial Undercurrent and topographic Rossby waves, respectively. Sediments, particularly in Mariana (422 ng g −1 dw), showed high OPE affinity, likely due to organic matter serving as a transport medium, influenced by "solvent switching", "solvent depletion", and "filtering processes". Amphipods in the three trenches had consistent OPE levels (29.1−215 ng g −1 lipid weight), independent of the sediment pollution patterns. The OPEs in these amphipods appeared more linked to surface-dwelling organisms, suggesting the influence of "solvent depletion". This study highlights the need for an improved understanding of deep-sea pollutant sources and transport, urging the establishment of protective measures for these remote marine habitats.

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“…The variations both within and between individual trenches are considerable, presumably due to local bathymetry, and spatiotemporal dynamics as induced by mass-wasting events. However, the sources and characteristics of the material reaching the trench axes are still poorly resolved (Lin et al, 2021;Luo et al, 2019;Xu et al, 2021). While the deposited organic material sustains high biological activity (Glud et al, 2021), it apparently also leads to considerable sequestration of organic material along the trench axes.…”

Section: Discussionmentioning

confidence: 99%

Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

Oguri

¹

,

Masqué

²

,

Zabel

³

et al. 2022

Preprint

0

View full text Add to dashboard Cite

Hadal trenches are considered to act as depocenters for organic material, although pathways for the material transport and deposition rates are poorly constrained. Here we assess focusing, deposition and accumulation of material and organic carbon in four hadal trench systems underlying different surface ocean productivities; the eutrophic Atacama and Kuril-Kamchatka trenches, the mesotrophic Kermadec trench and the oligotrophic Mariana Trench. The study is based on the distributions of naturally occurring 210 Pb ex , 137 Cs and total organic carbon from recovered sediment cores and by applying previously quantified benthic mineralization rates. Periods of steady deposition and discreet mass-wasting deposits were identified from the profiles and the latter were associated with historic recorded seismic events in the respective regions. During periods without mass wasting, the estimated focusing factors along trench axes were elevated, suggesting more or less continuous downslope focusing of material toward the interior of the trenches. The estimated organic carbon deposition rates during these periods exhibited extensive site-specific variability, but were generally similar to values encountered at much shallower settings such as continental slopes and margins. Organic carbon deposition rates during periods of steady deposition were not mirrored by surface ocean productivity, but appeared confounded by local bathymetry. The inclusion of deposition mediated by mass-wasting events enhanced the sediment and organic carbon accumulations for the past ∼150 years by up to a factor of ∼4. Thus, due to intensified downslope material focusing and infrequent mass-wasting events, hadal trenches are important sites for deposition and sequestration of organic carbon in the deep sea.Plain Language Summary Hadal trenches (>6,000 m water depth) occupy ∼1% of the world's ocean floor yet are largely underexplored, but recent studies have shown that these environments are depocenters for organic material and microbial activity is intensified when compared to shallower abyssal plains. However, transport and accumulation of sediment material to these hadal trenches is poorly understood. This study investigates sedimentation and accumulation dynamics of organic carbon in trenches using results of radionuclide analysis (in sediment from the Atacama, Kuril-Kamchatka, Kermadec, and Mariana trenches). The analysis shows that trench sediments consist of discreet layers representing both periods of continuous deposition and sudden mass-wasting events often triggered by historic earthquakes. Down slope focusing of material, intensified the deposition along the trench axes. However, the deposition rates exhibited extensive site-specific variations that were partly related to mass-wasting events which greatly enhanced not only mass accumulation but also organic carbon accumulation at the trench axes. Our results illustrate that mass-wasting events play an important role on supplying organic carbon to hadal communities and suggest that hadal tr...

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Geochemistry and mineralogy of the sediments in the New Britain shelf-trench continuum, offshore Papua New Guinea: Insights into sediment provenance and burial in hadal trenches

Cited by 7 publications

References 92 publications

Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

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

Sediment Accumulation and Carbon Burial in Four Hadal Trench Systems

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