Controls on the abundance, provenance and age of organic carbon buried in continental margin sediments

Ausín, Blanca; Bruni, Elena; Haghipour, Negar; Welte, Caroline; Bernasconi, Stefano M.; Eglinton, Timothy I.

doi:10.1016/j.epsl.2021.116759

Cited by 41 publications

(41 citation statements)

References 47 publications

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“…Sources and composition Burdige (2006), Canfield (1994), , Meyers (1997), Middelburg (2019) Oxygen exposure time (settling and burial) Hartnett et al (1998), Hoefs et al (2002), Sinninghe , Huguet et al (2008), Sun andWakeham (1994), Wakeham et al (1997) Terminal electron acceptor availability Aller (1994), Aller and Aller (1998), Canfield et al (1993), Canfield (1994) Microbial activity LaRowe et al (2020a, b), Stevenson et al (2020), Bradley et al (2020) Sediment biological mixing (bioturbation and bioirrigation) Aller (1980Aller ( , 1994, Aller and Aller (1998), Boudreau (1994), Grossi et al (2003), Middelburg (2018), Aller and Cochran (2019) Ageing and transport history Bianchi et al (2018), Cathalot et al (2010), Griffith et al (2010), Mollenhauer et al (2003Mollenhauer et al ( , 2007, Ohkouchi et al (2002), Ausín et al (2021) OM-sediment association Bianchi et al (2018), Hemingway et al (2019), Keil and Cowie (1999), Mayer (1994b, a) OM-iron mineral adsorption Salvadó et al (2015), Shields et al (2016), Wang et al (2019), Faust et al (2021) Priming van Nugteren et al (2009), Guenet et al (2010),…”

Section: Description Referencementioning

confidence: 99%

“…This is also reflected by the composition of the phytoplankton community and thus OM production at the photic zone and vertical transport efficiency to sediments (e.g. Bach et al, 2019). This wide spectrum of depositional environments (Tables 2 and S1) offers a unique opportunity to quantify OM reactivity and explore its multidisciplinary links with environmental drivers.…”

Section: Study Sitesmentioning

confidence: 99%

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New insights into large-scale trends of apparent organic matter reactivity in marine sediments and patterns of benthic carbon transformation

et al. 2021

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Abstract. Constraining the mechanisms controlling organic matter (OM) reactivity and, thus, degradation, preservation, and burial in marine sediments across spatial and temporal scales is key to understanding carbon cycling in the past, present, and future. However, we still lack a detailed quantitative understanding of what controls OM reactivity in marine sediments and, consequently, a general framework that would allow model parametrization in data-poor areas. To fill this gap, we quantify apparent OM reactivity (i.e. OM degradation rate constants) by extracting reactive continuum model (RCM) parameters (a and v, which define the shape and scale of OM reactivity profiles, respectively) from observed benthic organic carbon and sulfate dynamics across 14 contrasting depositional settings distributed over five distinct benthic provinces. We further complement the newly derived parameter set with a compilation of 37 previously published RCM a and v estimates to explore large-scale trends in OM reactivity. Our analysis shows that the large-scale variability in apparent OM reactivity is largely driven by differences in parameter a (10−3–107) with a high frequency of values in the range 100–104 years. In contrast, and in broad agreement with previous findings, inversely determined v values fall within a narrow range (0.1–0.2). Results also show that the variability in parameter a and, thus, in apparent OM reactivity is a function of the whole depositional environment, rather than traditionally proposed, single environmental controls (e.g. water depth, sedimentation rate, OM fluxes). Thus, we caution against the simplifying use of a single environmental control for predicting apparent OM reactivity beyond a specific local environmental context (i.e. well-defined geographic scale). Additionally, model results indicate that, while OM fluxes exert a dominant control on depth-integrated OM degradation rates across most depositional environments, apparent OM reactivity becomes a dominant control in depositional environments that receive exceptionally reactive OM. Furthermore, model results show that apparent OM reactivity exerts a key control on the relative significance of OM degradation pathways, the redox zonation of the sediment, and rates of anaerobic oxidation of methane. In summary, our large-scale assessment (i) further supports the notion of apparent OM reactivity as a dynamic ecosystem property, (ii) consolidates the distributions of RCM parameters, and (iii) provides quantitative constraints on how OM reactivity governs benthic biogeochemical cycling and exchange. Therefore, it provides important global constraints on the most plausible range of RCM parameters a and v and largely alleviates the difficulty of determining OM reactivity in RCM by constraining it to only one variable, i.e. the parameter a. It thus represents an important advance for model parameterization in data-poor areas.

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Section: Description Referencementioning

confidence: 99%

Section: Study Sitesmentioning

confidence: 99%

New insights into large-scale trends of apparent organic matter reactivity in marine sediments and patterns of benthic carbon transformation

et al. 2021

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“…The varied source contribution of OM toward this tropical coastal setting through riverine and/or land‐based runoff could be responsible for their relation and occurrences. It has also been reported that these local bulk signatures of TOC (e.g., C/N, δ 13 C) could be partially constrained by the translocation and redeposition of these specific silt fractions induced by the hydrodynamic sorting (Ausín et al., 2021; and Thimdee et al., 2003). There existed a correlation between grain size and terrestrial n ‐alkanes ( R 2 = 0.52, p < 0.01) (Figure 3d), suggesting a potential hydrodynamic force and/or source‐related constrains on the accumulation of the molecular components.…”

Section: Resultsmentioning

confidence: 99%

Impact of Source Variability and Hydrodynamic Forces on the Distribution, Transport, and Burial of Sedimentary Organic Matter in a Tropical Coastal Margin: The Gulf of Thailand

Bai

et al. 2021

JGR Biogeosciences

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More than 80% of organic carbon (OC) is buried in estuarine continental shelves, affecting the global carbon balance (Hedges & Keil, 1995). Therefore, the distribution, sources, and migration of sedimentary organic matter (SOM) on the continental shelves are important for understanding the source-to-sink processes Abstract Carbon cycling in the tropical margin is more extensive compared with other regions of the world. The goal of this study was to better understand the origins, transport, and burial of sedimentary organic matter (SOM) in the Gulf of Thailand (GOT) from the coastal margin of Southeast (SE) Asia, which serve as a major depository of fine-grained sediments and the associated organic carbon (OC). The results revealed a variety of organic matter (OM) inputs and the selective transport of fine sediment, resulting in preferential dispersal of terrigenous SOM in the GOT. Bulk OC indices with low carbon/ nitrogen ratios and enriched stable carbon isotope ratios (−24.2‰ to −20.4‰, and mean −21.4 ± 0.56‰) are likely related to the presence of marine-derived OM and anthropogenic interference. A binary mixing model further clarified the significant contributions of terrestrial derived-OM within the upper and central GOT. The n-alkane compositions and principal component analysis indicated that a majority of the terrigenous SOM settles within the estuary in the upper GOT, while a selective dispersal of land-based SOM through long-distance transport toward the modern depocenter in the lower GOT. The characteristics of lower molecular weight n-alkanes also suggest anthropogenic OM input from petroleum-related contributions. Altogether, the depositional patterns and spatial heterogeneity of the SOM indicated by both the bulk and molecular signatures reveal the important roles of source variability and the selective dispersal of land-based OM on the supply and accumulation of OC in the tropical coastal margin. Plain Language SummaryThe accumulation and fate of sedimentary organic carbon (OC) in the tropical coastal system are significant components of the global carbon cycling. In order to elucidate the distribution and accumulation of organic matter (OM) in tropical regimes, this study first explored the concentration and composition of sedimentary OC based on the bulk and molecular-level data, and then depicted the modern transport pattern of OM in the Gulf of Thailand (GOT). This study showed terrestrial input accounted for 5%-64% (20% ± 8% on average) of the OM and dominated in the upper GOT, the offshore depocenter in the northeastern GOT and north of Samui Island. Molecular composition of n-alkanes and principal component analysis result showed that the hydrodynamic condition plays a significant role on the selective dispersal of terrigenous OM from the coastal region to the offshore depocenter. In addition, the contribution from petroleum-derived OM is also revealed based on the molecular-level evidences. The spatial heterogeneity of OM revealed the variability of the sources and hydrodynamic forces on acc...

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“…Grain-size sediment fractions analysed by Ausín et al (2021) showed that OC associated with the silt fraction had higher radiocarbon ages compared to clayassociated OC in various continental margin settings. The substantial pre-aging of silt-associated OC is attributed to its tendency for resuspension and prolonged translocation as silt is generally considered non-cohesive (Ausín et al, 2021;McCave et al, 1995). Conversely, the clay fraction is considered cohesive and has been found to be associated with allochthonous OC, which is less pre-aged.…”

Section: Figure 5 |mentioning

confidence: 97%

“…In general, fine-grained detrital material such as clay contains relatively high amounts of K, whereas relatively high amounts of Ti are found in coarser sediments such as coarse silt and very fine sand (Bloemsma et al, 2012;Henares et al, 2019;Rothwell and Croudace, 2015). Grain-size sediment fractions analysed by Ausín et al (2021) showed that OC associated with the silt fraction had higher radiocarbon ages compared to clayassociated OC in various continental margin settings. The substantial pre-aging of silt-associated OC is attributed to its tendency for resuspension and prolonged translocation as silt is generally considered non-cohesive (Ausín et al, 2021;McCave et al, 1995).…”

Section: Figure 5 |mentioning

confidence: 99%

The Reservoir Age Effect Varies With the Mobilization of Pre-Aged Organic Carbon in a High-Altitude Central Asian Catchment

Schroeter

Mingram²,

Kalanke³

et al. 2021

Front. Earth Sci.

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Lake sediments provide excellent archives to study past environmental and hydrological changes at high temporal resolution. However, their utility is often restricted by chronological uncertainties due to the “reservoir age effect” (RAE), a phenomenon that results in anomalously old radiocarbon ages of total organic carbon (TOC) samples that is mainly attributed to the contribution of pre-aged carbon from aquatic organisms. Although the RAE is a well-known problem especially in high altitude lakes, detailed studies analyzing the temporal variations in the contribution of terrestrial and aquatic organic carbon (OC) on the RAE are scarce. This is partially due to the complexity of isolating individual compounds for subsequent compound-specific radiocarbon analysis (CSRA). We developed a rapid method for isolating individual short-chain (C16 and C18) and long-chain (>C24) saturated fatty acid methyl esters (FAMEs) by using high-pressure liquid chromatography (HPLC). Our method introduces only minor contaminations (0.50 ± 0.22 µg dead carbon on average) and requires only few injections (≤10), therefore offering clear advantages over traditional preparative gas chromatography (prep-GC). Here we show that radiocarbon values (Δ14C) of long-chain FAs, which originate from terrestrial higher plant waxes, reflect carbon from a substantially pre-aged OC reservoir, whereas the Δ14C of short-chain FAs that originate from aquatic sources were generally less pre-aged. 14C ages obtained from the long-chain FAs are in closer agreement with 14C ages of the corresponding bulk TOC fraction, indicating a high control of pre-aged terrestrial OC input from the catchment on TOC-derived 14C ages. Variations in the age offset between terrestrial and aquatic biomarkers are related to changes in bulk sediment log(Ti/K) that reflect variations in detrital input from the catchment. Our results indicate that the chronological offset between terrestrial and aquatic OC in this high-altitude catchment is mainly driven by temporal variations in the mobilization of pre-aged OC from the catchment. In conclusion, to obtain accurate and process-specific lake sediment chronologies, attention must be given to the temporal dynamics of the RAE. Variations in the apparent ages of aquatic and terrestrial contributions to the sediment and their mass balance can substantially alter the reservoir age effect.

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Controls on the abundance, provenance and age of organic carbon buried in continental margin sediments

Cited by 41 publications

References 47 publications

New insights into large-scale trends of apparent organic matter reactivity in marine sediments and patterns of benthic carbon transformation

New insights into large-scale trends of apparent organic matter reactivity in marine sediments and patterns of benthic carbon transformation

Impact of Source Variability and Hydrodynamic Forces on the Distribution, Transport, and Burial of Sedimentary Organic Matter in a Tropical Coastal Margin: The Gulf of Thailand

The Reservoir Age Effect Varies With the Mobilization of Pre-Aged Organic Carbon in a High-Altitude Central Asian Catchment

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