The influence of oxygen exposure time on the composition of macromolecular organic matter as revealed by surface sediments on the Murray Ridge (Arabian Sea)

Nierop, Klaas G.J.; Reichart, Gert‐Jan; Veld, Harry; Damsté, Jaap S. Sinninghe

doi:10.1016/j.gca.2017.02.032

Cited by 29 publications

(22 citation statements)

References 81 publications

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“…1; Wakeham et al, 1997;Dauwe et al, 1999;Lee et al, 2000). The proportion of organic matter that can be characterized molecularly decreases with progressive degradation, i.e., with water depth or depth downcore (Wakeham et al, 1997;Hedges et al, 2000;Middelburg et al, 1999;Nierop et al, 2017). This molecularly uncharacterizable material increases to more than 70 % of the total in deep-sea sediment organic matter.…”

Section: Organic Geochemists Focus On the Composition Of Organic Mattmentioning

confidence: 99%

“…The compositional changes have also been used to infer transformation of organic matter by bacteria (Cowie and Hedges, 1994;Dauwe et al, 1999;Grutters et al, 2001; Vandewiele et al, 2009;Lomstein et al, 2006Lomstein et al, , 2012, extent of degradation under oxic and anoxic conditions (Sinninghe Damsté et al, 2002;Huguet et al, 2008;Nierop et al, 2017), and the relative importance of bacteria and fauna for organic matter degradation (Sun et al, 1999;Woulds et al, 2012Woulds et al, , 2014. Although some organic geochemical studies hint at the importance of secondary production (Hayes et al, 1989;Cowie and Hedges, 1994;Grutters et al, 2001;Lomstein et al, 2006Lomstein et al, , 2012, this aspect has received little attention in organic geochemistry; however, it is one of the main objectives within the ecological approach.…”

Section: Organic Geochemists Focus On the Composition Of Organic Mattmentioning

confidence: 99%

“…During the last 2 decades, 13 C-labeled phytodetritus addition experiments have been performed to identify the organisms involved in the immediate processing of organic matter delivered to the seafloor (Middelburg, 2014). These studies often covered all size classes (animals and microbes) and could show that respiration was the major fate of added phytodetritus and that all size classes directly profited from recently deposited organic matter (Blair et al, 1996;Moodley et al, 2002Moodley et al, , 2005aWoulds et al, 2007Woulds et al, , 2009Woulds et al, , 2016Witte et al, 2003;Nomaki et al, 2005;Sweetman and Witte, 2008). In other words, heterotrophic microbes and small and big animals compete for the same food.…”

Section: Ecologists Focus On the Dynamics Of Organisms Using Organic mentioning

confidence: 99%

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Reviews and syntheses: to the bottom of carbon processing at the seafloor

2018

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Abstract. Organic carbon processing at the seafloor is studied by biogeochemists to quantify burial and respiration, by organic geochemists to elucidate compositional changes and by ecologists to follow carbon transfers within food webs. Here I review these disciplinary approaches and discuss where they agree and disagree. It will be shown that the biogeochemical approach (ignoring the identity of organisms) and the ecological approach (focussing on growth and biomass of organisms) are consistent on longer timescales.

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Section: Organic Geochemists Focus On the Composition Of Organic Mattmentioning

confidence: 99%

Section: Organic Geochemists Focus On the Composition Of Organic Mattmentioning

confidence: 99%

Section: Ecologists Focus On the Dynamics Of Organisms Using Organic mentioning

confidence: 99%

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Reviews and syntheses: to the bottom of carbon processing at the seafloor

2018

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“…The Murray Ridge represents an open ocean setting, and the selected coring sites were in close proximity to each other, with no substantial terrigenous contribution (Koho et al, 2013;Lengger et al, 2014Lengger et al, , 2012bNierop et al, 2017; Fig. 1d).…”

Section: Origin Of Sedimentary Organic Mattermentioning

confidence: 99%

Dark carbon fixation contributes to sedimentary organic carbon in the Arabian Sea oxygen minimum zone

Lengger¹,

Rush²,

Mayser³

et al. 2019

Preprint

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In response to rising CO2 concentrations and increasing global sea surface temperatures, oxygen minimum zones (OMZ), or “dead zones”, are expected to expand. OMZs are fueled by high primary productivity, resulting in enhanced biological oxygen demand at depth, subsequent oxygen depletion, and attenuation of remineralization. This results in the deposition of organic carbon-rich sediments. Carbon drawdown is estimated by biogeochemical models; however, a major process is ignored: carbon fixation in the mid- and lower water column. Here, we show that chemoautotrophic carbon fixation is important in the Arabian Sea OMZ; and manifests in a 13C-depleted signature of sedimentary organic carbon. We determined the δ13C values of SOM deposited in close spatial proximity but over a steep bottom-water oxygen gradient, and the δ13C composition of biomarkers of chemoautotrophic bacteria capable of anaerobic ammonia oxidation (anammox). Isotope mixing models show that detritus from anammox bacteria or other chemoautotrophs likely forms a substantial part of the organic matter deposited within the Arabian Sea OMZ (~17%), implying that the contribution of chemoautotrophs to settling organic matter is exported to the sediment. This has implications for the evaluation of past, and future, OMZs: biogeochemical models that operate on the assumption that all sinking organic matter is photosynthetically derived, without new addition of carbon, could significantly underestimate the extent of remineralization. Oxygen demand in oxygen minimum zones could thus be higher than projections suggest, leading to a more intense expansion of OMZs than expected.

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“…These contributing OM fractions exist on a scale of recalcitrance that is complicated by environmental factors that can augment a macromolecule's inherent recalcitrance. Chemical stabilization (Mayer, 1995), physical protection (Keil et al, 1994), anaerobic metabolism (Nierop et al, 2017), nutrient limitation (Enriquez et al, 1993;Lopez et al, 1998), and unachieved energetic thresholds can limit microbially-driven degradation and remineralization, thus changing the realized recalcitrance of OM. Blue Carbon discussions often consider the recalcitrance of seagrass soil C org as dependent on the stable, low nutrient, anoxic environmental in which it is buried rather than inherent properties of the OM , though this may be an oversimplification given the complicated mixtures of organic compounds that make up soil C org and the complex environmental factors that influence the refractory nature of each of those compounds.…”

Section: Discussionmentioning

confidence: 99%

Patterns of Carbon Metabolism, Storage, and Remineralization in Seagrass Ecosystems

Howard¹

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Coastal marine sediments have recently been identified as globally important stocks of organic carbon (C org) that, if compromised, could significantly exacerbate global greenhouse gas emissions. While resource managers and policy makers are eager to incorporate this ecosystem service into seagrass ecosystem valuation frameworks, similar to those already in existence for terrestrial forests, there has been insufficient information regarding how environmental conditions and seagrass ecology control carbon storage. These include the influence of the seagrass to the production and preservation of soil organic matter, the fate of stored carbon following conversion of coastal wetlands, and the interactions between organic and inorganic carbon cycling. This dissertation intends to to understand the drivers of C org storage and preservation to better prioritize and evaluate the worth of seagrasses to large scale carbon cycles and greenhouse gas mitigation planning. Long-term experiments and thorough field surveys reveal that seagrasses are not categorically necessary nor sufficient for long-term C org storage. Soil C org stocks as well as their recalcitrance and breakdown rates are all correlated with sediment grain size, where muddy, fine sediments have higher C org stocks that are less likely to breakdown. Sediment grain size can be influenced by the presence of seagrasses at some sites, likely where the leaf canopy can modify local hydrology enough to create a depositional environmental that wouldn't otherwise exist. However, similar depositional environments that collect and v store C org can be obtained through local geomorphological features and natural hydrology, independent of benthic flora. This distinction has important implications on how soil C is managed to continue its preservation. The relation between seagrass C org and CO 2 can be blurred by calcification and carbonate dissolution processes that occur concurrently, and have direct but antagonistic effects on CO 2. Carbonate processes are dependent on local environmental factors, though augmented by biological processes, thus the ability of carbonate processes to interfere with seagrass C org storage and loss is limited to geographic areas where processes can occur. Warm, shallow waters, like those in Florida Bay, encourage calcification, though the magnitude of soil inorganic and organic carbon interaction can vary locally as well. Seagrasses are declining globally thus additional ecosystem value via greenhouse gas mitigation could greatly benefit conservation efforts. To make conservation efforts worthwhile to greenhouse gas mitigation, these findings help to consider and prioritize sites where risk and impact of C org lost is more severe. vi

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The influence of oxygen exposure time on the composition of macromolecular organic matter as revealed by surface sediments on the Murray Ridge (Arabian Sea)

Cited by 29 publications

References 81 publications

Reviews and syntheses: to the bottom of carbon processing at the seafloor

Reviews and syntheses: to the bottom of carbon processing at the seafloor

Dark carbon fixation contributes to sedimentary organic carbon in the Arabian Sea oxygen minimum zone

Patterns of Carbon Metabolism, Storage, and Remineralization in Seagrass Ecosystems

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