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                                       Details for article 123 of 144 found articles
 
 
  Spatial variability of phytoplankton pigment distributions in the Subtropical South Pacific Ocean: comparison between in situ and predicted data
 
 
Title: Spatial variability of phytoplankton pigment distributions in the Subtropical South Pacific Ocean: comparison between in situ and predicted data
Author: J. Ras
H. Claustre
J. Uitz
Appeared in: Biogeosciences discussions
Paging: Volume 4 (2007) nr. 5 pages 3409-3451
Year: 2007
Contents: In the frame of the BIOSOPE cruise in 2004, the spatial distribution and structure of phytoplankton pigments was investigated along a transect crossing the ultra-oligotrophic South Pacific Subtropical Gyre (SPSG) between the Marquesas Archipelago (141° W–8° S) and the Chilean upwelling (73° W–34° S). A High Performance Liquid Chromatography (HPLC) method was improved in order to be able to accurately quantify pigments over such a large range of trophic levels, and especially the strongly oligotrophic conditions. Seven diagnostic pigments were associated to three phytoplankton size classes (pico-, nano and microphytoplankton). The total chlorophyll <I>a</I> (TChl<I>a</I>) concentrations in surface waters were the lowest measured in the centre of the gyre, reaching 0.017 mg m<sup>−3. Pigment concentrations at the Deep Chlorophyll Maximum (DCM) were generally 10 fold the surface values. Results were compared to predictions from a global parameterisation based on remotely sensed surface TChl<I>a</I> concentrations. The agreement between the in situ and predicted data for such contrasting phytoplankton assemblages was generally good: throughout the oligotrophic gyre system, picophytoplankton (prochlorophytes and cyanophytes) was a dominant class, the nanophytoplankton signature was also significant and relative bacteriochlorophyll <I>a</I> concentrations varied around 2%. The transition zone between the Marquesas and the SPSG was also well predicted by the model. However, some regional particularities have been observed where measured and modelled data differ. Amongst these features is the extreme depth of the DCM (180 m) towards the centre of the gyre, the presence of a deep nanoflagellate population beneath the DCM or the presence of a prochlorophyte-enriched population in the high salinity formation area of the South Pacific Tropical Water. A coastal site sampled in the eutrophic upwelling zone, characterised by recently upwelled water, was significantly and unusually enriched in picoeucaryotes, in contrast with the offshore upwelling site where a more typical senescent diatom population was dominant.
Publisher: Copernicus GmbH (provided by DOAJ)
Source file: Elektronische Wetenschappelijke Tijdschriften
 
 

                             Details for article 123 of 144 found articles
 
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