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      Response of the larger protozooplankton to an iron-induced phytoplankton bloom in the Polar Frontal Zone of the Southern Ocean (EisenEx)

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      General Information:

      Citation:
      Henjes, J. , Assmy, P. , Klaas, C. and Smetacek, V. (2007): Response of the larger protozooplankton to an iron-induced phytoplankton bloom in the Polar Frontal Zone of the Southern Ocean (EisenEx) , Deep Sea Research I: Oceanographic Research Papers:, 54 (5), pp. 774-791 . doi: 10.1016/j.dsr.2007.02.005
      Cite this page as:
      hdl:10013/epic.26353
      DOI:
      10.1016/j.dsr.2007.02.005
      Official URL:
      10.1016/j.dsr.2007.02.005
      Contact Email:
      Joachim.Henjes@awi.de
      Related Data:

      Platform/Expeditions:
      • ANT-XVIII/2
      Abstract:

      The responses of larger (>50 μm in diameter) protozooplankton groups to a phytoplankton bloom induced by in situ iron fertilization (EisenEx) in the Polar Frontal Zone (PFZ) of the Southern Ocean in austral spring are presented. During the 21 days of the experiment, samples were collected from seven discrete depths in the upper 150 m inside and outside the fertilized patch for the enumeration of acantharia, foraminifera, radiolaria, heliozoa, tintinnid ciliates and aplastidic thecate dinoflagellates. Inside the patch, acantharian numbers increased twofold, but only negligibly in surrounding waters. This finding is of major interest, since 30 acantharia are suggested to be involved in the formation of barite (BaSO4), a palaeoindicator of both ancient and modern high productivity regimes. Foraminifera increased significantly in abundance inside and outside the fertilized patch. However, the marked increase of juveniles after a full moon event suggests a lunar periodicity in the reproduction cycle of some foraminiferan species rather than a reproductive response to enhanced food availability. In contrast, adult radiolaria showed no clear trend during the experiment, but juveniles increased threefold, indicating elevated reproduction. Aplastidic thecate dinoflagellates almost doubled in numbers and biomass but also increased outside the patch. Tintinnid numbers decreased twofold, although biomass remained constant because of a shift in the size spectrum. Empty tintinnid loricae, however, increased by a factor of two, indicating that grazing pressure on 40 this group mainly by copepods, intensified during EisenEx. The results show that ironfertilization experiments can shed light on the biology and the role of these larger protists in pelagic ecosystem, which will improve their use as proxies in paleoceanography.

      Further Details:

      Item Type:
      Article
      Authors:
      Henjes, Joachim ; Assmy, Philipp ; Klaas, Christine ; Smetacek, Victor
      Divisions:
      AWI Organizations > Biosciences > Polar Biological Oceanography
      Programs:
      Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL-MARCOPOLI
      Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL2-Southern Ocean climate and ecosystem
      Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL5-Autecology of planktonic key species and groups
      Eprint ID:
      16425
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