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  • Elsevier  (5)
  • Public Library of Science
  • 2005-2009  (5)
  • 1
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    Investigating the effect of ballasting by CaCO3 in Emiliania huxleyi, II: Decomposition of particulate organic matter (2009)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 56 (18). pp. 1408-1419.
    Details
    Publication Date: 2020-03-19
    Description: The quantitative relationship between organic carbon and mineral contents of particles sinking below 1800 m in the ocean indicates that organisms with mineral shells such as coccolithophores are of special importance for transporting carbon into the deep sea. Several hypotheses about the mechanism behind this relationship between minerals and organic matter have been raised, such as mineral protection of organic matter or enhanced sinking rates through ballast addition. We examined organic matter decomposition of calcifying and non-calcifying Emiliania huxleyi cultures in an experiment that allowed aggregation and settling in rotating tanks. Biogenic components such as particulate carbon, particulate nitrogen, particulate volume, pigments, transparent exopolymer particles (TEP), and particulate amino acids in suspended particles and aggregates were followed over a period of 30 d. The overall pattern of decrease in organic matter, the amount of recalcitrant organic matter left after 30 d, and the compositional changes within particulate organic matter indicated that cells without a shell are more subject to loss than calcified cells. It is suggested that biogenic calcite helps in the preservation of particulate organic matter (POM) by offering structural support for organic molecules. Over the course of the experiment, half the particulate organic carbon in both calcifying and non-calcifying cultures was partitioned into aggregates and remained so until the end of the experiment. The partial protection of particulate organic matter from solubilization by biominerals and by aggregation that was observed in our experiment may help explain the robustness of the relationship between organic and mineral matter fluxes in the deep ocean.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr2.2008.11.028
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    MedFlux: Investigations of particle flux in the Twilight Zone (2009)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 56 (18). pp. 1363-1368.
    Details
    Publication Date: 2020-03-20
    Description: The MedFlux project was devised to determine and model relationships between organic matter and mineral ballasts of sinking particulate matter in the ocean. Specifically we investigated the ballast ratio hypothesis, tested various commonly used sampling and modeling techniques, and developed new technologies that would allow better characterization of particle biogeochemistry. Here we describe the rationale for the project, the biogeochemical provenance of the DYFAMED site, the international support structure, and highlights from the papers published here. Additional MedFlux papers can be accessed at the MedFlux web site (http://msrc.sunysb.edu/MedFlux/).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr2.2008.12.003
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Abundance and size distribution of transparent exopolymer particles (TEP) in a coccolithophorid bloom in the northern Bay of Biscay (2009)
    Elsevier
    In:  Deep-Sea Research Part I-Oceanographic Research Papers, 56 (8). pp. 1251-1265.
    Details
    Publication Date: 2020-03-20
    Description: The distribution of transparent exopolymer particles (TEP) was investigated during a coccolithophorid bloom in the northern Bay of Biscay (North Atlantic Ocean) in early June 2006. MODIS chlorophyll-a (Chl-a) and reflectance images before and during the cruise were used to localize areas of important biological activity and high reflectance (HR). TEP profiles along the continental margin, determined using microscopic (TEPmicro) and colorimetric (TEPcolor) methods, showed abundant (6.1×106–4.4×107 L−1) and relatively small (0.5–20 μm) particles, leading to a low total volume fraction (0.05–2.2 ppm) of TEPmicro and similar vertical profiles of TEPcolor. Estimates of carbon content in TEP (TEP-C) derived from the microscopic approach yielded surface concentration of 1.50 μmol C L−1. The contribution of TEP-C to particulate organic carbon (POC) was estimated to be 12% (molar C ratio) during this survey. Our results suggest that TEP formation is a probable first step to rapid and efficient export of C during declining coccolithophorid blooms.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr.2009.01.014
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Investigating the effect of ballasting by CaCO3 in Emiliania huxleyi: I. Formation, settling velocities and physical properties of aggregates (2009)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 56 (18). pp. 1396-1407.
    Details
    Publication Date: 2020-03-19
    Description: To investigate the role of ballasting by biogenic minerals in the export of organic matter in the ocean, a laboratory experiment was conducted comparing aggregate formation and settling velocity of non-calcifying and calcifying strains of the coccolithophore Emiliania huxleyi. Experiments were conducted by making aggregates using a roller table and following aggregate properties during incubation for a period of 40 days. Size, shape, and settling velocities of aggregates were described by image analysis of video pictures recorded during the roller tank incubation. Our results show that biogenic calcite has a strong effect on the formation rate and abundance of aggregates and on aggregate properties such as size, excess density, porosity, and settling velocity. Aggregates of calcifying cells (AGGCAL) formed faster, were smaller and had higher settling velocities, excess densities, and mass than those of non-calcifying cells (AGGNCAL). AGGCAL showed no loss during the duration of the experiment, whereas AGGNCAL decreased in size after 1 month of incubation. Potential mechanisms that can explain the different patterns in aggregate formation are discussed. Comparison of settling velocities of AGGCAL and AGGNCAL with aggregates formed by diatoms furthermore indicated that the ballast effect of calcite is greater than that of opal. Together these results help to better understand why calcite is of major importance for organic matter fluxes to the deep ocean.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr2.2008.11.027
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  • 5
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    Carbon isotopic fractionation during a mesocosm bloom experiment dominated by Emiliania huxleyi: Effects of CO2 concentration and primary production (2007)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 71 . pp. 1528-1541.
    Details
    Publication Date: 2019-09-23
    Description: We investigated the effect of CO2 and primary production on the carbon isotopic fractionation of alkenones and particulate organic matter (POC) during a natural phytoplankton bloom dominated by the coccolithophore Emiliania huxleyi. In nine semi-closed mesocosms (~11 m3 each), three different CO2 partial pressures (pCO2) in triplicate represented glacial (~180 ppmv CO2), present (~380 ppmv CO2), and year 2100 (~710 ppmv CO2) CO2 conditions. The largest shift in alkenone isotopic composition (4–5&) occurred during the exponential growth phase, regardless of the CO2 concentration in the respective treatment. Despite the difference of ~500 ppmv, the influence of pCO2 on isotopic fractionation was marginal (1–2&). During the stationary phase, E. huxleyi continued to produce alkenones, accumulating cellular concentrations almost four times higher than those of exponentially dividing cells. Our isotope data indicate that, while alkenone production was maintained, the interaction of carbon source and cellular uptake dynamics by E. huxleyi reached a steady state. During stationary phase, we further observed a remarkable increase in the difference between d13C of bulk organic matter and of alkenones spanning 7–12&. We suggest that this phenomenon is caused mainly by a combination of extracellular release of 13C-enriched polysaccharides and subsequent particle aggregation induced by the production of transparent exopolymer particles (TEP). 2007 Elsevier Inc. All rights reserved.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2006.12.015
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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