Poulton Alex J.

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Poulton
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Alex J.
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  • Article
    The possession of coccoliths fails to deter microzooplankton grazers
    (Frontiers Media, 2020-12-02) Mayers, Kyle M. J. ; Poulton, Alex J. ; Bidle, Kay D. ; Thamatrakoln, Kimberlee ; Schieler, Brittany ; Giering, Sarah L. C. ; Wells, Seona R. ; Tarran, Glen A. ; Mayor, Daniel J. ; Johnson, Matthew D. ; Riebesell, Ulf ; Larsen, Aud ; Vardi, Assaf ; Harvey, Elizabeth L.
    Phytoplankton play a central role in the regulation of global carbon and nutrient cycles, forming the basis of the marine food webs. A group of biogeochemically important phytoplankton, the coccolithophores, produce calcium carbonate scales that have been hypothesized to deter or reduce grazing by microzooplankton. Here, a meta-analysis of mesocosm-based experiments demonstrates that calcification of the cosmopolitan coccolithophore, Emiliania huxleyi, fails to deter microzooplankton grazing. The median grazing to growth ratio for E. huxleyi (0.56 ± 0.40) was not significantly different among non-calcified nano- or picoeukaryotes (0.71 ± 0.31 and 0.55 ± 0.34, respectively). Additionally, the environmental concentration of E. huxleyi did not drive preferential grazing of non-calcified groups. These results strongly suggest that the possession of coccoliths does not provide E. huxleyi effective protection from microzooplankton grazing. Such indiscriminate consumption has implications for the dissolution and fate of CaCO3 in the ocean, and the evolution of coccoliths.
  • Article
    Does a ballast effect occur in the surface ocean?
    (American Geophysical Union, 2010-04-29) Sanders, Richard J. ; Morris, Paul J. ; Poulton, Alex J. ; Stinchcombe, Mark C. ; Charalampopoulou, Anastasia ; Lucas, Mike I. ; Thomalla, Sandy J.
    The oceanic biological carbon pump (BCP), a large (10 GT C yr−1) component of the global carbon cycle, is dominated by the sinking (export) of particulate organic carbon (POC) from surface waters. In the deep ocean, strong correlations between downward fluxes of biominerals and POC (the so-called ‘ballast effect’) suggest a potential causal relationship, the nature of which remains uncertain. We show that similar correlations occur in the upper ocean with high rates of export only occurring when biominerals are also exported. Exported particles are generally biomineral rich relative to the upper ocean standing stock, due either to: (1) exported material being formed from the aggregation of a biomineral rich subset of upper ocean particles; or (2) the unfractionated aggregation of the upper ocean particulate pool with respiration then selectively removing POC relative to biominerals until particles are dense enough to sink.
  • Article
    A compilation of global bio-optical in situ data for ocean-colour satellite applications - version two
    (Copernicus Publications, 2019-07-15) Valente, André ; Sathyendranath, Shubha ; Brotas, Vanda ; Groom, Steven ; Grant, Michael ; Taberner, Malcolm ; Antoine, David ; Arnone, Robert ; Balch, William M. ; Barker, Kathryn ; Barlow, Ray ; Belanger, Simon ; Berthon, Jean-François ; Besiktepe, Sukru ; Borsheim, Yngve ; Bracher, Astrid ; Brando, Vittorio ; Canuti, Elisabetta ; Chavez, Francisco P. ; Cianca, Andrés ; Claustre, Hervé ; Clementson, Lesley ; Crout, Richard ; Frouin, Robert ; García-Soto, Carlos ; Gibb, Stuart W. ; Gould, Richard ; Hooker, Stanford B. ; Kahru, Mati ; Kampel, Milton ; Klein, Holger ; Kratzer, Susanne ; Kudela, Raphael M. ; Ledesma, Jesus ; Loisel, Hubert ; Matrai, Patricia A. ; McKee, David ; Mitchell, Brian G. ; Moisan, Tiffany ; Muller-Karger, Frank E. ; O'Dowd, Leonie ; Ondrusek, Michael ; Platt, Trevor ; Poulton, Alex J. ; Repecaud, Michel ; Schroeder, Thomas ; Smyth, Timothy ; Smythe-Wright, Denise ; Sosik, Heidi M. ; Twardowski, Michael ; Vellucci, Vincenzo ; Voss, Kenneth ; Werdell, Jeremy ; Wernand, Marcel ; Wright, Simon ; Zibordi, Giuseppe
    A global compilation of in situ data is useful to evaluate the quality of ocean-colour satellite data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (including, inter alia, MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID, AMT, ICES, HOT and GeP&CO) and span the period from 1997 to 2018. Observations of the following variables were compiled: spectral remote-sensing reflectances, concentrations of chlorophyll a, spectral inherent optical properties, spectral diffuse attenuation coefficients and total suspended matter. The data were from multi-project archives acquired via open internet services or from individual projects, acquired directly from data providers. Methodologies were implemented for homogenization, quality control and merging of all data. No changes were made to the original data, other than averaging of observations that were close in time and space, elimination of some points after quality control and conversion to a standard format. The final result is a merged table designed for validation of satellite-derived ocean-colour products and available in text format. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) was propagated throughout the work and made available in the final table. By making the metadata available, provenance is better documented, and it is also possible to analyse each set of data separately. This paper also describes the changes that were made to the compilation in relation to the previous version (Valente et al., 2016). The compiled data are available at https://doi.org/10.1594/PANGAEA.898188 (Valente et al., 2019).
  • Article
    A compilation of global bio-optical in situ data for ocean-colour satellite applications
    (Copernicus Publications on behalf of the European Geosciences Union, 2016-06-03) Valente, André ; Sathyendranath, Shubha ; Brotas, Vanda ; Groom, Steven ; Grant, Michael ; Taberner, Malcolm ; Antoine, David ; Arnone, Robert ; Balch, William M. ; Barker, Kathryn ; Barlow, Ray ; Belanger, Simon ; Berthon, Jean-François ; Besiktepe, Sukru ; Brando, Vittorio ; Canuti, Elisabetta ; Chavez, Francisco P. ; Claustre, Hervé ; Crout, Richard ; Frouin, Robert ; García-Soto, Carlos ; Gibb, Stuart W. ; Gould, Richard ; Hooker, Stanford B. ; Kahru, Mati ; Klein, Holger ; Kratzer, Susanne ; Loisel, Hubert ; McKee, David ; Mitchell, Brian G. ; Moisan, Tiffany ; Muller-Karger, Frank E. ; O'Dowd, Leonie ; Ondrusek, Michael ; Poulton, Alex J. ; Repecaud, Michel ; Smyth, Timothy ; Sosik, Heidi M. ; Twardowski, Michael ; Voss, Kenneth ; Werdell, Jeremy ; Wernand, Marcel ; Zibordi, Giuseppe
    A compiled set of in situ data is important to evaluate the quality of ocean-colour satellite-data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID, AMT, ICES, HOT, GeP&CO), span between 1997 and 2012, and have a global distribution. Observations of the following variables were compiled: spectral remote-sensing reflectances, concentrations of chlorophyll a, spectral inherent optical properties and spectral diffuse attenuation coefficients. The data were from multi-project archives acquired via the open internet services or from individual projects, acquired directly from data providers. Methodologies were implemented for homogenisation, quality control and merging of all data. No changes were made to the original data, other than averaging of observations that were close in time and space, elimination of some points after quality control and conversion to a standard format. The final result is a merged table designed for validation of satellite-derived ocean-colour products and available in text format. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) were preserved throughout the work and made available in the final table. Using all the data in a validation exercise increases the number of matchups and enhances the representativeness of different marine regimes. By making available the metadata, it is also possible to analyse each set of data separately. The compiled data are available at doi:10.1594/PANGAEA.854832 (Valente et al., 2015).