Transfer of organic carbon through marine water columns to sediments – insights from stable and radiocarbon isotopes of lipid biomarkers

Wakeham, Stuart G.; McNichol, Ann P.

doi:10.5194/bg-11-6895-2014

Cited by 30 publications

(27 citation statements)

References 112 publications

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“…sinking POC) had a δ 13 C value of ‐22.4 ‰ (composite of the OMZ between 500 and 900 m depth). The corresponding sedimentary δ 13 C org value, from oxygenated bottom waters at 1445 m depth, was, however, more enriched (‐20.8‰; Wakeham & McNichol, ). Fernandes et al () detected similar, though less pronounced, trends in sediments collected from the Pakistan margin.…”

Section: Discussionmentioning

confidence: 99%

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

Lengger

Rush

Mayser

et al. 2019

Global Biogeochemical Cycles

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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 Corg 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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Section: Discussionmentioning

confidence: 99%

“…In line with an anammox origin, BHT' here is decidedly more depleted than other biomarkers in the Arabian Sea (cf. Wakeham & McNichol, ), though distinctly depleted highly branched isoprenoids (HBIs, ‐37 ‰) have been found in Arabian Sea cores from the Holocene (Schouten et al, ).…”

Section: Discussionmentioning

confidence: 99%

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

Lengger

Rush

Mayser

et al. 2019

Global Biogeochemical Cycles

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“…Surface sediments of river-dominated margins typically exhibit significant variability in OC radiocarbon ( 14 C OC ) content (Bao et al, 2016;Bianchi et al, 2016;Canuel & Hardison, 2016;Griffith et al, 2010;Wakeham & McNichol, 2014 • Supporting Information S1…”

Section: Introductionmentioning

confidence: 99%

Influence of Hydrodynamic Processes on the Fate of Sedimentary Organic Matter on Continental Margins

Bao

Voort

Zhao

et al. 2018

Global Biogeochemical Cycles

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Understanding the effects of hydrodynamic forcing on organic matter (OM) composition is important for assessment of organic carbon (OC) burial in marginal seas on regional and global scales. Here we examine the relationships between regional oceanographic conditions (bottom shear stress), and the physical characteristics (mineral surface area and grain size) and geochemical properties (OC content [OC%] and carbon isotope compositions [13C, 14C]) of a large suite of surface sediments from the Chinese marginal seas to assess the influence of hydrodynamic processes on the fate of OM on shallow continental shelves. Our results suggest that 14C content is primarily controlled by organo‐mineral interactions and hydrodynamically driven resuspension processes, highlighted by (i) positive correlations between 14C content and OC% (and surface area) and (ii) negative correlations between 14C content and grain size (and bottom shear stress). Hydrodynamic processes influence 14C content due to both OC aging during lateral transport and accompanying selective degradation of OM associated with sediment (re) mobilization, these effects being superimposed on the original 14C characteristics of carbon source. Our observations support the hypotheses of Blair and Aller (2012, https://doi.org/10.1146/annurev-marine-120709-142717) and Leithold et al. (2016, https://doi.org/10.1016/j.earscirev.2015.10.011) that hydrodynamically driven sediment translocation results in greater OC 14C depletion in broad, shallow marginal seas common to passive margin settings than on active margins. On a global scale, this may influence the extent to which continental margins act as net carbon sources and sinks. Our findings thus suggest that hydrodynamic processes are important in shaping the nature, dynamics, and magnitude of OC export and burial in passive marginal seas.

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“…When released to aquatic environments, plastic particles lighter than the surrounding media float and are transported by the water. A combination of physio-chemical and biological mechanisms drive the transport of microplastics from surface waters to sediments (Wakeham and McNichol 2014;Taylor et al 2016;Kaiser et al 2017;Porter et al 2018). In coastal regions, plastic particles are prone to high-energy processes, such as waves, tides, and wind, which cause vertical mixing or surface drifting until final deposition in beach sediments (Zhang 2017).…”

Section: Microbe-mediated Transport Of Plasticmentioning

confidence: 99%

Micro-by-Micro Interactions: How Microorganisms Influence the Fate of Marine Microplastics

Carreres‐Calabuig¹,

Rogers²,

Gorokhova³

et al. 2019

Preprint

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Microorganisms drive the biogeochemical cycles that link abiotic and biotic processes in the aqueous environment and are intricately associated with plastic debris. The detection of microplastics in water and sediment introduces new concerns as small particle size allows for yet unconsidered pathways for plastics in the food web and element cycles. In this review, we present current knowledge of microbe-plastic interactions and summarize the potential impact of biogeochemical processes on plastic distribution, cycling, transport, and sedimentation. We explore how microbe-plastic interactions influence the exposure of consumers to plastics and plastic degradation products. Key methods used to elucidate biofilm development, microbial biodegradation, and plastic detection in the aqueous environment are discussed. Finally, we comment on potential future questions and research directions needed to further define the role of microorganisms in the environmental fate of microplastics.

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Transfer of organic carbon through marine water columns to sediments – insights from stable and radiocarbon isotopes of lipid biomarkers

Cited by 30 publications

References 112 publications

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

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

Influence of Hydrodynamic Processes on the Fate of Sedimentary Organic Matter on Continental Margins

Micro-by-Micro Interactions: How Microorganisms Influence the Fate of Marine Microplastics

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