Publications by authors named "Geoffrey D Abbott"

8 Publications

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Transformation of organic matter in a Barents Sea sediment profile: coupled geochemical and microbiological processes.

Philos Trans A Math Phys Eng Sci 2020 Oct 31;378(2181):20200223. Epub 2020 Aug 31.

School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.

Process-based, mechanistic investigations of organic matter transformation and diagenesis directly beneath the sediment-water interface (SWI) in Arctic continental shelves are vital as these regions are at greatest risk of future change. This is in part due to disruptions in benthic-pelagic coupling associated with ocean current change and sea ice retreat. Here, we focus on a high-resolution, multi-disciplinary set of measurements that illustrate how microbial processes involved in the degradation of organic matter are directly coupled with inorganic and organic geochemical sediment properties (measured and modelled) as well as the extent/depth of bioturbation. We find direct links between aerobic processes, reactive organic carbon and highest abundances of bacteria and archaea in the uppermost layer (0-4.5 cm depth) followed by dominance of microbes involved in nitrate/nitrite and iron/manganese reduction across the oxic-anoxic redox boundary (approx. 4.5-10.5 cm depth). Sulfate reducers dominate in the deeper (approx. 10.5-33 cm) anoxic sediments which is consistent with the modelled reactive transport framework. Importantly, organic matter reactivity as tracked by organic geochemical parameters (-alkanes, -alkanoic acids, -alkanols and sterols) changes most dramatically at and directly below the SWI together with sedimentology and biological activity but remained relatively unchanged across deeper changes in sedimentology. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.
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http://dx.doi.org/10.1098/rsta.2020.0223DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7481670PMC
October 2020

Does Arctic warming reduce preservation of organic matter in Barents Sea sediments?

Philos Trans A Math Phys Eng Sci 2020 Oct 31;378(2181):20190364. Epub 2020 Aug 31.

School of Earth and Environment, The University of Leeds, Leeds, UK.

Over the last few decades, the Barents Sea experienced substantial warming, an expansion of relatively warm Atlantic water and a reduction in sea ice cover. This environmental change forces the entire Barents Sea ecosystem to adapt and restructure and therefore changes in pelagic-benthic coupling, organic matter sedimentation and long-term carbon sequestration are expected. Here we combine new and existing organic and inorganic geochemical surface sediment data from the western Barents Sea and show a clear link between the modern ecosystem structure, sea ice cover and the organic carbon and CaCO contents in Barents Sea surface sediments. Furthermore, we discuss the sources of total and reactive iron phases and evaluate the spatial distribution of organic carbon bound to reactive iron. Consistent with a recent global estimate we find that on average 21.0 ± 8.3 per cent of the total organic carbon is associated to reactive iron (fOC-Fe) in Barents Sea surface sediments. The spatial distribution of fOC-Fe, however, seems to be unrelated to sea ice cover, Atlantic water inflow or proximity to land. Future Arctic warming might, therefore, neither increase nor decrease the burial rates of iron-associated organic carbon. However, our results also imply that ongoing sea ice reduction and the associated alteration of vertical carbon fluxes might cause accompanied shifts in the Barents Sea surface sedimentary organic carbon content, which might result in overall reduced carbon sequestration in the future. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.
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http://dx.doi.org/10.1098/rsta.2019.0364DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7481662PMC
October 2020

Benthic-pelagic coupling in the Barents Sea: an integrated data-model framework.

Philos Trans A Math Phys Eng Sci 2020 Oct 31;378(2181):20190359. Epub 2020 Aug 31.

BGeosys, Department of Earth and Environmental Sciences, CP 160/02, Université Libre de Bruxelles, 1050 Brussels, Belgium.

The Barents Sea is experiencing long-term climate-driven changes, e.g. modification in oceanographic conditions and extensive sea ice loss, which can lead to large, yet unquantified disruptions to ecosystem functioning. This key region hosts a large fraction of Arctic primary productivity. However, processes governing benthic and pelagic coupling are not mechanistically understood, limiting our ability to predict the impacts of future perturbations. We combine field observations with a reaction-transport model approach to quantify organic matter (OM) processing and disentangle its drivers. Sedimentary OM reactivity patterns show no gradients relative to sea ice extent, being mostly driven by seafloor spatial heterogeneity. Burial of high reactivity, marine-derived OM is evident at sites influenced by Atlantic Water (AW), whereas low reactivity material is linked to terrestrial inputs on the central shelf. Degradation rates are mainly driven by aerobic respiration (40-75%), being greater at sites where highly reactive material is buried. Similarly, ammonium and phosphate fluxes are greater at those sites. The present-day AW-dominated shelf might represent the future scenario for the entire Barents Sea. Our results represent a baseline systematic understanding of seafloor geochemistry, allowing us to anticipate changes that could be imposed on the pan-Arctic in the future if climate-driven perturbations persist. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.
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http://dx.doi.org/10.1098/rsta.2019.0359DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7481668PMC
October 2020

Cretaceous dinosaur bone contains recent organic material and provides an environment conducive to microbial communities.

Elife 2019 06 18;8. Epub 2019 Jun 18.

Department of Geosciences, Princeton University, Princeton, United States.

Fossils were thought to lack original organic molecules, but chemical analyses show that some can survive. Dinosaur bone has been proposed to preserve collagen, osteocytes, and blood vessels. However, proteins and labile lipids are diagenetically unstable, and bone is a porous open system, allowing microbial/molecular flux. These 'soft tissues' have been reinterpreted as biofilms. Organic preservation versus contamination of dinosaur bone was examined by freshly excavating, with aseptic protocols, fossils and sedimentary matrix, and chemically/biologically analyzing them. Fossil 'soft tissues' differed from collagen chemically and structurally; while degradation would be expected, the patterns observed did not support this. 16S rRNA amplicon sequencing revealed that dinosaur bone hosted an abundant microbial community different from lesser abundant communities of surrounding sediment. Subsurface dinosaur bone is a relatively fertile habitat, attracting microbes that likely utilize inorganic nutrients and complicate identification of original organic material. There exists potential post-burial taphonomic roles for subsurface microorganisms.
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http://dx.doi.org/10.7554/eLife.46205DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6581507PMC
June 2019

Exploring the geochemical distribution of organic carbon in early land plants: a novel approach.

Philos Trans R Soc Lond B Biol Sci 2018 Feb;373(1739)

School of Natural and Environmental Sciences, Newcastle University, Ridley Building, Newcastle upon Tyne NE1 7RU, UK.

Terrestrialization depended on the evolution of biosynthetic pathways for biopolymers including lignin, cutin and suberin, which were concentrated in specific tissues, layers or organs such as the xylem, cuticle and roots on the submillimetre scale. However, it is often difficult, or even impossible especially for individual cells, to resolve the biomolecular composition of the different components of fossil plants on such a scale using the well-established coupled techniques of gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry. Here, we report the application of techniques for surface analysis to investigate the composition of X-ray photoelectron spectroscopy of two different spots (both 300 µm × 600 µm) confirmed the presence of carbon. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed 'chemical maps' (imaging mode with 300 nm resolution) of aliphatic and aromatic carbon in the intact fossil that correlate with the vascular structures observed in high-resolution optical images. This study shows that imaging ToF-SIMS has value for determining the location of the molecular components of fossil embryophytes while retaining structural information that will help elucidate how terrestrialization shaped the early evolution of land plant cell wall biochemistry.This article is part of a discussion meeting issue 'The Rhynie cherts: our earliest terrestrial ecosystem revisited'.
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http://dx.doi.org/10.1098/rstb.2016.0499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5745335PMC
February 2018

Determination of Asphaltene Critical Nanoaggregate Concentration Region Using Ultrasound Velocity Measurements.

Sci Rep 2017 11 23;7(1):16125. Epub 2017 Nov 23.

Newcastle University, School of Natural and Environmental Sciences, Newcastle upon Tyne, NE1 7RU, United Kingdom.

Asphaltenes constitute the heaviest, most polar and aromatic fraction of petroleum crucial to the formation of highly-stable water-in-crude oil emulsions. The latter occur during crude oil production as well as spills and cause difficulties to efficient remediation practice. It is thought that in nanoaggregate form, asphaltenes create elastic layers around water droplets enhancing stability of the emulsion matrix. Ultrasonic characterisation is a high-resolution non-invasive tool in colloidal analysis shown to successfully identify asphaltene nanoaggregation in toluene. The high sensitivity of acoustic velocity to molecular rearrangements and ease in implementation renders it an attractive method to study asphaltene phase properties. Currently, aggregation is thought to correspond to an intersection of two concentration-ultrasonic velocity regressions. Our measurements indicate a variation in the proximity of nanoaggregation which is not accounted for by present models. We attribute this uncertainty to physico-chemical heterogeneity of the asphaltene fraction driven by variation in molecular size and propose a critical nanoaggregation region. We treated asphaltenes from North and South American crude oils with ruthenium ion catalysed oxidation to characterize their n-alkyl appendages attached to aromatic cores. Principal component analysis was performed to investigate the coupling between asphaltene structures and velocity measurements and their impact on aggregation.
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http://dx.doi.org/10.1038/s41598-017-16294-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5700960PMC
November 2017

Deterioration of the Hanson Logboat: chemical and imaging assessment with removal of polyethylene glycol conserving agent.

Sci Rep 2017 10 20;7(1):13697. Epub 2017 Oct 20.

Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.

The state of preservation of wood in two samples from the Hanson Logboat, currently on display in Derby Museum and Art Gallery, was analysed using elemental analysis (EA), pyrolysis-gas chromatography/flame ionisation detection (Py-GC/FID), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and scanning electron microscopy (SEM). The samples were collected in 2003, after the boat had undergone conservation, and in 2011 after the condition of the boat began to deteriorate. Solvent extraction enabled removal of polyethylene glycol, with which the wood had been impregnated during conservation, allowing the degradation of the cellulose and lignin polymeric components of the woods to be assessed. Elemental compositions (C, H, N, O, S), Py-GC/FID, Py-GC/MS and SEM imaging reveal extensive degradation of the wood polymers during the eight year period since conservation.
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http://dx.doi.org/10.1038/s41598-017-14057-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651872PMC
October 2017

Contrasting temperature responses of dissolved organic carbon and phenols leached from soils.

Plant Soil 2016;399:13-27. Epub 2015 Sep 23.

School of Civil Engineering and Geosciences, Drummond Building, Newcastle University, Newcastle-upon-Tyne, NE1 7RU UK.

Background And Aims: Plant-derived phenols are a major input to the terrestrial carbon cycle that might be expected to contribute substantially to dissolved organic carbon (DOC) losses from soils. This study investigated changes in DOC and phenols in leachates from soil treated with individual plant litter types under seasonal temperature change.

Methods: Senescing grass, buttercup, ash and oak litters were applied to soil lysimeters. Leachates were collected over 22 months and analysed for DOC and phenols. Phenols in litter and DOC were analysed using on-line thermally assisted hydrolysis and methylation with tetramethylammonium hydroxide (TMAH).

Results: Mass loss differed between litter type (buttercup>ash>grass>oak). Phenol concentrations in the senescing litters (<2 % TOC) were small, resulting in minor losses to water. Seasonal soil temperature positively correlated with DOC loss from litter-free soils. An initial correlation between temperature change and total phenol concentration in grass and ash litter treatment leachates diminished with time. Dissolved phenol variety in all litter-amended soil leachates increased with time.

Conclusions: Plant-derived phenols from senescing litter made a minor contribution to DOC loss from soils. The strength of the relationship between seasonal temperature change and phenol type and abundance in DOC changed with time and was influenced by litter type.
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http://dx.doi.org/10.1007/s11104-015-2678-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4750429PMC
September 2015