Elena Bruni


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Bruni

First Name

Elena

ORCID

0000-0003-4490-3298

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2022 - 20237
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Publications 1 - 7 of 7
  • ISODRAPES: Spatial Variability in the Provenance, Vintage and Quality of Organic Carbon accumulating on the Ocean Floor
    Item type: Other Conference Item
    Eglinton, Timothy Ian; Paradis, Sarah; Gies, Hannah; et al. (2022)
    The cycling and burial of organic matter (OM) on continental margins is relevant to a broad range of topics including benthic-pelagic coupling, seafloor biodiversity, sedimentological processes, paleoclimate reconstruction, marine bio- (fisheries) and geo- (mining) resources, and carbon stocktaking. Carbon cycling over continental margins is highly dynamic and spatially heterogeneous, resulting in complex patterns in the content and composition of OM as well as the mineralogical and granulometric characteristics of underlying sediments. Improved assessment of the factors leading to the role and sensitivity of organic carbon (OC) burial requires comprehensive understanding of OC sources as well the processes that influence its fate. To address this issue, we are synthesizing available geochemical and sedimentological data, and combining this information with new measurements in a nascent margin-centric surface sediment database, MOSAIC. In particular, we focus on ¹⁴C measurements as a means to constrain OC supply and dispersal over continental margins. We will highlight the strong hydrodynamic and mineralogical controls on the distribution and composition of sedimentary organic matter, and the pervasive influence of lateral transport processes on continental margins. Ultimately, we seek to derive a more spatially-nuanced view of the amount, nature and age of organic matter accumulating in continental margin sediments and its role in the global carbon cycle.
  • Grain size specific authigenic Nd isotope compositions in the Northwest Atlantic Ocean – Ubiquity of authigenic phases and impacts of boundary exchange processes
    Item type: Other Conference Item
    Rickli, Jörg; Tallon, Marie; Bamberg, Cédric; et al. (2023)
    Goldschmidt 2023 Abstract
  • Clay dissolution during early diagenesis? – Insights from neodymium isotopes
    Item type: Conference Poster
    Rickli, Jörg; Tallon, Marie; Bamberg, Cedric; et al. (2022)
  • Sedimentary hydrodynamic processes under low-oxygen conditions
    Item type: Conference Poster
    Bruni, Elena; Blattmann, Thomas; Haghipour, Negar; et al. (2022)
    Continental margin sediments represent a major global sink of organic carbon (OC), and exert a key control on Earth’s climate. Today, OC burial in marine sediments mainly takes place under oxygen-rich water columns, where most OC is intimately associated with sediment grains and biogenic minerals. In prior episodes of Earth’s past, when large parts of the oceans were anoxic, the mode of sedimentary OC burial must have been very different, however. Present-day analogues indicate that surface sediments accumulating under low-oxygen water columns are often “soupy” in texture. Moreover, most OC occurs in large (100 - 2,000 μm diameter) organic and organo-mineral aggregates which, due to their low density, are prone to wave- and current-induced resuspension. Upon mobilization, these aggregates can undergo lateral transport within so-called nepheloid layers, and may be translocated hundreds of kilometres, and on timescales of thousands of years. Little is known about processes of formation, resuspension and hydrodynamic properties of these aggregates, or which factors control their eventual breakdown or burial. The goal of this study is to examine the drivers and biogeochemical consequences of this resuspension on OC cycling in modern, oxygen-depleted, “Semi-Liquid Ocean Bottom” (SLOB) areas. We argue that models of sediment and OM hydrodynamics and redistribution that describe sedimentation processes in oxygenated ocean waters of the modern ocean are a poor analogue for equivalent processes occurring under oxygen-deficient conditions. In the latter, we hypothesize that (a) the abundance of low-density organic-rich particles and aggregates leads to a greater propensity for sediment remobilization at low(er) shear stress, and (b) upon resuspension into low-oxygen bottom waters, remobilized OM may be subject to less degradation (less attenuation) during lateral transport, leading to efficient and widespread translocation to distal centres of deposition. We address specific aspects of the SLOB hypothesis utilizing a combination of literature and new data, focussing on the Benguela Upwelling Region as a model system.
  • A Semi-Liquid Ocean Bottom Hypothesis: hydrodynamic controls on organic carbon distribution in oxygen-deficient settings
    Item type: Doctoral Thesis
    Bruni, Elena (2023)
    The thesis project lies at the interface of biogeochemistry, microbiology, and sedimentology, a combination which has not been applied in this context yet. It centres on the Semi-Liquid Ocean Bottom-hypothesis (SLOB), which states that the accumulation of organic matter in low-oxygen settings results in a “soupy” surface sediment texture where most organic carbon is present in large aggregates with minimal mineral content. Occurring in abundance in local depocenters, these lowdensity particles will influence sediment hydrodynamic properties and lower the critical threshold of motion. In addition, such settings often sustain a flocculent layer suspended over the more compacted sedimentary layer. Its preferential displacement initiates repeated resettlingresuspension cycles at already low-energy events, often forming bottom nepheloid layers. These are hotspots of microbial activity, which opens the question about whether the lower threshold of motion of OC-rich sediment and its repeated reintroduction into biologically active zones may significantly influence whether a sedimentary environment represents a sink or source of carbon to the environment. Moreover, lateral transport of organic matter has become a hot topic of discussion in paleoceanography after increasing numbers of studies report asynchronous records in coexisting organic proxies, which may compromise how we understand organic carbon storage in the global ocean. This project aims at identifying the conditions necessary to initiate the dislocation process and frame its extent on a regional scale. This study focuses on fifteen globally distributed, primarily marine, oxygen-deficient settings, where the potential for resuspension, lateral transport, and the concurrent ageing of organic carbon is investigated using a novel combinatory approach. Experimental assays on surface sediments aim to test and reconstruct erosion resistance and response to current motion. The subsequent application of a traditional biogeochemical toolset and radiocarbon measurements on different sedimentary categories (e.g., grain size fractions or density fractions) allows for approximating the individual study sites’ potential for the transport of sedimentary organic carbon. The implications of this study are intricate but universally applicable to any field of research that handles surface sediments of high organic carbon content. In brief, the results that emerged from this thesis project highlight the care that must be taken in interpreting any sedimentary record of such nature.
  • Testing the Semi-Liquid Ocean Bottom (SLOB) hypothesis
    Item type: Presentation
    Bruni, Elena; Blattmann, Thomas; Haghipour, Negar; et al. (2022)
    Continental margin sediments represent a major global sink of organic carbon (OC), and exert a key control on Earth’s climate. Today, OC burial in marine sediments mainly takes place under oxygen-rich water columns, where most OC is intimately associated with sediment grains and biogenic minerals. In prior episodes of Earth’s past, when large parts of the oceans were anoxic, the mode of sedimentary OC burial must have been very different, however. Present-day analogues indicate that surface sediments accumulating under low-oxygen water columns are often “soupy” in texture. Moreover, most OC occurs in large (100 - 2,000 μm diameter) organic and organo-mineral aggregates which, due to their low density, are prone to wave- and current-induced resuspension. Upon mobilization, these aggregates can undergo lateral transport within so-called nepheloid layers, and may be translocated hundreds of kilometres, and on timescales of thousands of years. Little is known about processes of formation, resuspension and hydrodynamic properties of these aggregates, or which factors control their eventual breakdown or burial. The goal of this study is to examine the drivers and biogeochemical consequences of this resuspension on OC cycling in modern, oxygen-depleted, “Semi-Liquid Ocean Bottom” (SLOB) areas. We argue that models of sediment and OM hydrodynamics and redistribution that describe sedimentation processes in oxygenated ocean waters of the modern ocean are a poor analogue for equivalent processes occurring under oxygen-deficient conditions. In the latter, we hypothesize that (a) the abundance of low-density organic-rich particles and aggregates leads to a greater propensity for sediment remobilization at low(er) shear stress, and (b) upon resuspension into low-oxygen bottom waters, remobilized OM may be subject to less degradation (less attenuation) during lateral transport, leading to efficient and widespread translocation to distal centres of deposition. We address specific aspects of the SLOB hypothesis utilizing a combination of literature and new data, focussing on the Benguela Upwelling Region as a model system.
  • Organic matter coating defines threshold of motion in natural sediments
    Item type: Conference Poster
    Bruni, Elena; Blattmann, Thomas; Haghipour, Negar; et al. (2022)
    The onset of sediment erosion in is governed by sediment properties such as grain size, density, and environmental controls such as current strength. Investigating the relevance of each of these parameters has been an ongoing part of experimental sedimentology, resulting in several empirical threshold of motion curves [1,2]. These are used for different geotechnical applications, but so far, none of these include the effects of organic matter (OM) on particle motion, a draw-back that has been identified early on and limits the applicability in natural systems [e.g., 3]. We perform sediment erosion experiments on natural, untreated OM-rich sediments to investigate the impact of high OM concentrations on the sediment threshold of motion. Six sediment cores from Swiss lakes were inserted to EROMES, a resuspension chamber using a propeller to produce and control shear stress [4,5]. By incrementally increasing propeller rotation rates, the first and second erosion thresholds were identified. Measuring OC (%) revealed the fluff eroded at er I has higher concentrations than the suspended particles at er II and consists of labile aggregates and free OM (e.g., leaves). Moreover, the presence of benthic organisms (tube worms) resulted in a measurable strengthening of the sediment surface. The measurements of er I and II are plotted against calibration measurements performed with standardized (quartz) grains of known grain size distribution, which reveals the lower threshold of motion of particles associated with OM. Consequently, we argue for the recalibration of threshold motion curves to include low-density, OM-rich particles and the stabilising effects of benthic organisms [6]. Key words: SLOB hypothesis, sediment threshold of motion, organic matter, EROMES erosion chamber [1] A. Shields, Anwendung der Ähnlichkeitsmechanik und der Turbulenzforschung auf die Geschiebebewegung, Technische Hochschule Berlin, 1936. [2] F. Hjulström, Studies of the Morphological Activity of Rivers as Illustrated by the River Fyris, Geogr. Ann. 18 (1936) 121. https://doi.org/10.2307/519824. [3] M.C. Miller, I.N. McCave, P.D. Komar, Threshold of sediment motion under unidirectional currents, Sedimentology. 24 (1977) 507–527. https://doi.org/10.1111/j.1365-3091.1977.tb00136.x. [4] T.J. Andersen, E.J. Houwing, M. Pejrup, On the erodibility of fine-grained sediments in an infilling freshwater system, in: Proc. Mar. Sci., Elsevier B.V., 2002: pp. 315–328. https://doi.org/10.1016/S1568-2692(02)80024-9. [5] T.J. Tolhurst, K.S. Black, D.M. Paterson, H.J. Mitchener, G.R. Termaat, S.A. Shayler, A comparison and measurement standardisation of four in situ devices for determining the erosion shear stress of intertidal sediments, Cont. Shelf Res. 20 (2000) 1397–1418. https://doi.org/10.1016/S0278-4343(00)00029-7. [6] E.T. Bruni, T.M. Blattmann, N. Haghipour, D. Louw, M. Lever, T.I. Eglinton, Sedimentary Hydrodynamic Processes Under Low-Oxygen Conditions: Implications for Past, Present, and Future Oceans, Front. Earth Sci. 10 (2022) 1–18. https://doi.org/10.3389/feart.2022.886395.
Publications 1 - 7 of 7