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  • 11
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    Particulate organic carbon deconstructed: molecular and chemical composition of particulate organic carbon in the ocean (2020)
    Frontiers Media
    Details
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kharbush, J. J., Close, H. G., Van Mooy, B. A. S., Arnosti, C., Smittenberg, R. H., Le Moigne, F. A. C., Mollenhauer, G., Scholz-Boettcher, B., Obreht, I., Koch, B. P., Becker, K. W., Iversen, M. H., & Mohr, W. Particulate organic carbon deconstructed: molecular and chemical composition of particulate organic carbon in the ocean. Frontiers in Marine Science, 7, (2020): 518, doi:10.3389/fmars.2020.00518.
    Description: The dynamics of the particulate organic carbon (POC) pool in the ocean are central to the marine carbon cycle. POC is the link between surface primary production, the deep ocean, and sediments. The rate at which POC is degraded in the dark ocean can impact atmospheric CO2 concentration. Therefore, a central focus of marine organic geochemistry studies is to improve our understanding of POC distribution, composition, and cycling. The last few decades have seen improvements in analytical techniques that have greatly expanded what we can measure, both in terms of organic compound structural diversity and isotopic composition, and complementary molecular omics studies. Here we provide a brief overview of the autochthonous, allochthonous, and anthropogenic components comprising POC in the ocean. In addition, we highlight key needs for future research that will enable us to more effectively connect diverse data sources and link the identity and structural diversity of POC to its sources and transformation processes.
    Description: We thank the Hanse Institute for Advanced Studies (HWK) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) project number 422798570, as well as the Geochemical Society, for funding which made the workshop possible. CA was additionally supported by OCE-1736772. BV was additionally supported by NSF OCE-1756254.
    Keywords: Marine particles ; Water column ; Phytoplankton ; Marine microbes ; Structural analysis ; Organic matter characterization ; Biomarkers
    Repository Name: Woods Hole Open Access Server
    Type: Article
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    PAPER (OA)
  • 12
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    On the effect of low oxygen concentrations on bacterial degradation of sinking particles (2017)
    Nature Research
    In:  Scientific Reports, 7 (1). Art. No. 16722.
    Details
    Publication Date: 2020-06-18
    Description: In marine oxygen (O2) minimum zones (OMZs), the transfer of particulate organic carbon (POC) to depth via the biological carbon pump might be enhanced as a result of slower remineralisation under lower dissolved O2 concentrations (DO). In parallel, nitrogen (N) loss to the atmosphere through microbial processes, such as denitrification and anammox, is directly linked to particulate nitrogen (PN) export. However it is unclear (1) whether DO is the only factor that potentially enhances POC transfer in OMZs, and (2) if particle fluxes are sufficient to support observed N loss rates. We performed a degradation experiment on sinking particles collected from the Baltic Sea, where anoxic zones are observed. Sinking material was harvested using surface-tethered sediment traps and subsequently incubated in darkness at different DO levels, including severe suboxia (〈0.5 mg l−1 DO). Our results show that DO plays a role in regulating POC and PN degradation rates. POC(PN) degradation was reduced by approximately 100% from the high to low DO to the lowest DO. The amount of NH4+ produced from the pool of remineralising organic N matched estimations of NH4+ anammox requirements during our experiment. This anammox was likely fueled by DON degradation rather than PON degradation.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/s41598-017-16903-3
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 13
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    The GEOTRACES Intermediate Data Product 2017 (2018)
    Elsevier
    In:  Chemical Geology, 493 . pp. 210-223.
    Details
    Publication Date: 2021-02-08
    Description: The GEOTRACES Intermediate Data Product 2017 (IDP2017) is the second publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2016. The IDP2017 includes data from the Atlantic, Pacific, Arctic, Southern and Indian oceans, with about twice the data volume of the previous IDP2014. For the first time, the IDP2017 contains data for a large suite of biogeochemical parameters as well as aerosol and rain data characterising atmospheric trace element and isotope (TEI) sources. The TEI data in the IDP2017 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at crossover stations. The IDP2017 consists of two parts: (1) a compilation of digital data for more than 450 TEIs as well as standard hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing an on-line atlas that includes more than 590 section plots and 130 animated 3D scenes. The digital data are provided in several formats, including ASCII, Excel spreadsheet, netCDF, and Ocean Data View collection. Users can download the full data packages or make their own custom selections with a new on-line data extraction service. In addition to the actual data values, the IDP2017 also contains data quality flags and 1-σ data error values where available. Quality flags and error values are useful for data filtering and for statistical analysis. Metadata about data originators, analytical methods and original publications related to the data are linked in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2017 as section plots and rotating 3D scenes. The basin-wide 3D scenes combine data from many cruises and provide quick overviews of large-scale tracer distributions. These 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of tracer plumes near ocean margins or along ridges. The IDP2017 is the result of a truly international effort involving 326 researchers from 22 countries. This publication provides the critical reference for unpublished data, as well as for studies that make use of a large cross-section of data from the IDP2017.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.chemgeo.2018.05.040
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 14
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    Iron Biogeochemistry in the High Latitude North Atlantic Ocean (2018)
    Nature Research
    In:  Scientific Reports, 8 (1283).
    Details
    Publication Date: 2021-04-21
    Description: Iron (Fe) is an essential micronutrient for marine microbial organisms, and low supply controls productivity in large parts of the world’s ocean. The high latitude North Atlantic is seasonally Fe limited, but Fe distributions and source strengths are poorly constrained. Surface ocean dissolved Fe (DFe) concentrations were low in the study region (〈0.1 nM) in summer 2010, with significant perturbations during spring 2010 in the Iceland Basin as a result of an eruption of the Eyjafjallajökull volcano (up to 2.5 nM DFe near Iceland) with biogeochemical consequences. Deep water concentrations in the vicinity of the Reykjanes Ridge system were influenced by pronounced sediment resuspension, with indications for additional inputs by hydrothermal vents, with subsequent lateral transport of Fe and manganese plumes of up to 250–300 km. Particulate Fe formed the dominant pool, as evidenced by 4–17 fold higher total dissolvable Fe compared with DFe concentrations, and a dynamic exchange between the fractions appeared to buffer deep water DFe. Here we show that Fe supply associated with deep winter mixing (up to 103 nmol m−2 d−1) was at least ca. 4–10 times higher than atmospheric deposition, diffusive fluxes at the base of the summer mixed layer, and horizontal surface ocean fluxes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/s41598-018-19472-1
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 15
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    Influence of iron, cobalt, and vitamin B12 supply on phytoplankton growth in the tropical East Pacific during the 2015 El Niño (2018)
    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 45 (12). pp. 6150-6159.
    Details
    Publication Date: 2021-04-23
    Description: Iron (Fe), cobalt (Co), and vitamin B12 addition experiments were performed in the eastern Equatorial Pacific/Peruvian upwelling zone during the 2015 El Niño event. Near the Peruvian coastline, apparent photosystem II photochemical efficiencies (Fv/Fm) were unchanged by nutrient addition and chlorophyll‐a tripled in untreated controls over two days, indicating nutrient replete conditions. Conversely, Fe amendment further away from the coastline in the high nitrate, low Fe zone significantly increased Fv/Fm and chlorophyll‐a concentrations. Mean chlorophyll‐a was further enhanced following supply of Fe+Co and Fe+B12 relative to Fe alone, but this was not statistically significant; further offshore, reported Co depletion relative to Fe could enhance responses. The persistence of Fe limitation in this system under a developing El Niño, as previously demonstrated under non‐El Niño conditions, suggests that diminished upwelled Fe is likely an important factor driving reductions in offshore phytoplankton productivity during these events.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1029/2018GL077972
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 16
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    Recent evolution of 129 I levels in the Nordic Seas and the North Atlantic Ocean (2018)
    Elsevier
    In:  Science of the Total Environment, 621 . pp. 376-386.
    Details
    Publication Date: 2021-02-08
    Description: Most of the anthropogenic radionuclide 129I released to the marine environment from the nuclear fuel reprocessing plants (NFRP) at Sellafield (England) and La Hague (France) is transported to the Arctic Ocean via the North Atlantic Current and the Norwegian Coastal Current. 129I concentrations in seawater provides a powerful and well-established radiotracer technique to provide information about the mechanisms which govern water mass transport in the Nordic Seas and the Arctic Ocean and is gaining importance when coupled with other tracers (e.g. CFC, 236U). In this work, 129I concentrations in surface and depth profiles from the Nordic Seas and the North Atlantic (NA) Ocean collected from four different cruises between 2011 and 2012 are presented. This work allowed us to i) update information on 129I concentrations in these areas, required for the accurate use of 129I as a tracer of water masses; and ii) investigate the formation of deep water currents in the eastern part of the Nordic Seas, by the analysis of 129I concentrations and temperature-salinity (T-S) diagrams from locations within the Greenland Sea Gyre. In the Nordic Seas, 129I concentrations in seawater are of the order of 109 at·kg− 1, one or two orders of magnitude higher than those measured at the NA Ocean, not so importantly affected by the releases from the NFRP. 129I concentrations of the order of 108 atoms·kg− 1 at the Ellet Line and the PAP suggest a direct contribution from the NFRP in the NA Ocean. An increase in the concentrations in the Nordic Seas between 2002 and 2012 has been detected, which agrees with the temporal evolution of the 129I liquid discharges from the NFRPs in years prior to this. Finally, 129I profile concentrations, 129I inventories and T-S diagrams suggest that deep water formation occurred in the easternmost area of the Nordic Seas during 2012.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.scitotenv.2017.11.268
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 17
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    Biodegradation of Emiliania huxleyi aggregates by a natural Mediterranean prokaryotic community under increasing hydrostatic pressure (2018)
    Elsevier
    In:  Progress in Oceanography, 163 . pp. 271-281.
    Details
    Publication Date: 2021-02-08
    Description: In the deep ocean, fluxes of particulate organic carbon (POC) and calcium carbonate are positively correlated, suggesting that CaCO3 could increase sinking particle densities and/or protect the organic matter from degradation by prokaryotes, the so called “ballast effect”. Here, we used the PArticle Sinking Simulator (PASS) system to investigate the effect of increasing pressure on the biodegradation of calcifying Emiliania huxleyi aggregates. Incubations were carried out over a period of 10 days, simulating the changes in temperature and pressure in the water column of the NW Mediterranean Sea. Aggregates sinking from a depth of 200 m to 1700 m (assuming an average sinking velocity of 150 m d−1) were exposed to a natural mesopelagic prokaryotic community collected from 200 m. In contrast to previous studies, where silicifying diatom aggregates were used, the calcifying E. huxleyi aggregates were found to be more sensitive to degradation with increasing hydrostatic pressure (relative to constant atmospheric pressure). This was confirmed by changes in lipid composition which suggested increased cell lysis. Changes in particulate inorganic carbon and total alkalinity indicated that CaCO3 dissolution might have been faster under pressure. Increased hydrostatic pressure also had a positive effect on particle aggregation, which may compensate for the effect of increased cell lysis. Our results imply that in coccolithophorid-dominated sinking aggregates, the ballasting and protection effects of coccoliths may collapse throughout the water column. The increased aggregation potential with pressure observed in these controlled conditions, may balance the loss of mineral ballast to a certain extent, although this needs to be confirmed in situ.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.pocean.2017.01.005
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 18
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    234 Th-Derived Particle Fluxes and Seasonal Variability: When Is the SS Assumption Reliable? Insights From a Novel Approach for Carbon Flux Simulation (2018)
    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 45 (24). 13,414-13,426.
    Details
    Publication Date: 2021-02-08
    Description: 234Th measurements are widely used to estimate the downward carbon flux of particles via the oceanic Biological Pump. Carbon export is evaluated from 234Th-238U disequilibrium assuming either steady state (SS) conditions, or including a non-SS (NSS) correction. We use a novel stochastic simulation to quantify the temporal variation of vertical carbon and 234Th (dissolved and particulate) concentration profiles with high temporal resolution. We calculate seasonal export as if in situ measured with sediment trap and SS- and NSS-234Th approaches and quantify the periods of validity for SS/NSS conditions defined in previous works. The SS approach is valid throughout the entire season in oligotrophic regions. In temperate regions, the SS introduces a bias in the export if sampling takes place outside specific temporal windows. Windows of validity range from days in short blooms of ~15-day duration to weeks in blooms longer than ~30 days.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2018GL079968
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 19
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    Geographical, seasonal, and depth variation in sinking particle speeds in the North Atlantic (2016)
    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 43 (16). pp. 8609-8616.
    Details
    Publication Date: 2019-02-01
    Description: Particle sinking velocity is considered to be a controlling factor for carbon transport to the deep sea and thus carbon sequestration in the oceans. The velocities of the material exported to depth are considered to be high in high-latitude productive systems and low in oligotrophic distributions. We use a recently developed method based on the measurement of the radioactive pair 210Po-210Pb to calculate particle sinking velocities in the temperate and oligotrophic North Atlantic during different bloom stages. Our estimates of average sinking velocities (ASVs) show that slowly sinking particles (〈100 m d−1) contribute significantly to carbon flux at all the locations except in the temperate regions during the bloom. ASVs appear to vary strongly with season, which we propose is caused by changes in the epipelagic community structure. Our results are the first field data to confirm the long-standing theory that particle sinking velocities increase with depth, with increases of up to 90% between 50 and 150 m depth.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2016GL069233
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 20
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    Influence of bloom dynamics on Particle Export Efficiency in the North Atlantic: a comparative study of radioanalytical techniques and sediment traps (2016)
    Elsevier
    In:  Marine Chemistry, 186 . pp. 198-210.
    Details
    Publication Date: 2019-02-01
    Description: Highlights: • Performances of 3 methods to obtain POC flux and export efficiency are examined. • Bloom dynamics and sampling date must be associated to the method time scale. • Discrepancies between PEALAGRA, 234Th and 210Po methods are satisfactory interpreted. • Seasonal variability of the export efficiency in the North Atlantic is detected. Abstract: The Biological Carbon Pump is an important component of the global carbon cycle is (BCP). Particle Export Efficiency (PEeff), defined as the proportion of primary production (PP) exported as Particulate Organic Carbon (POC) from the surface ocean, is increasingly used as a metric of the strength of the BCP. However our knowledge of which factors drive variability of PEeff remains poor. This is partially because comparisons of PEeff in different regions often overlook the timescale over which the method used operates in relation to the phase of the plankton bloom. Here we use three techniques to estimate PEeff in situ in the North Atlantic: the radioactive pairs 238U-234Th and 210Pb-210Po, and neutrally buoyant sediment traps (PELAGRA). Order of magnitude discrepancies between values of PEeff obtained from PELAGRA relative to those obtained when applying both radionuclide techniques. POC export fluxes and satellite-derived PP suggest that this results from the differing time scales covered by the three methods and the timing of observations relative to the bloom peak. None of the three techniques are considered inappropriate to estimate PEeff in situ, but bloom dynamics must be considered in relation to the duration over which a particular sampling method operates. Our results suggest a strong seasonal variability in PEeff, most likely controlled by the community structure and hydrographic conditions. This implies that the methods used (specifically their inherent timescales) and the phase of the bloom at the time of sampling must be carefully taken into account to ensure that individual PEeff estimates compiled from different sources to construct global export algorithms are comparable.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.1016/j.marchem.2016.10.001
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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