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Aquatic Microbial Ecology

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AME 70:215-232 (2013)  -  DOI:

Microzooplankton grazing along the Western Antarctic Peninsula

Lori M. Garzio1,*, Deborah K. Steinberg1,*, Matthew Erickson2, Hugh W. Ducklow3

1Virginia Institute of Marine Science, College of William & Mary, PO Box 1346, Gloucester Pt., Virginia 23062, USA
2Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
3Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA
*Corresponding authors.  Email: ;

ABSTRACT: The significance of microzooplankton as grazers in pelagic ecosystems has been established, yet relatively few studies of microzooplankton grazing, compared to that of macrozooplankton, have been conducted in the Southern Ocean. We report phytoplankton and bacterial growth and grazing mortality rates along the Western Antarctic Peninsula (WAP), a region of rapid climate change. Growth and grazing rates were determined by dilution experiments at select stations along the WAP in January of 2009 to 2011 and in the nearshore waters near Palmer Station in February and March 2011. Microzooplankton exerted higher grazing pressure on bacteria compared to phytoplankton along the WAP and also selectively grazed on smaller phytoplankton (picoautotrophs and nanophytoplankton) and on the more actively growing (high nucleic acid) bacterial cells. Among all phytoplankton size classes, growth rates ranged from undetectable (i.e. not significant; NS) to 0.99 d-1, grazing mortality rates were NS to 0.56 d-1, and microzooplankton removed <100% of daily phytoplankton production in all but one experiment. For high and low nucleic acid content bacteria, growth rates were NS to 0.95 d-1, and grazing mortality rates were NS to 0.43 d-1; microzooplankton often removed >100% of daily bacterial production. There was a significant (albeit weak) exponential relationship between temperature and phytoplankton mortality, although the range of experimental temperatures was small. The present study provides a reference point of microzooplankton grazing impact along the WAP in the summer and contributes valuable information to studies modeling the flow of carbon through the WAP food web, improving our ability to predict climate-induced changes in the WAP ecosystem.

KEY WORDS: Microzooplankton · Protozoa · Grazing · Western Antarctic Peninsula · Southern Ocean · Climate

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Cite this article as: Garzio LM, Steinberg DK, Erickson M, Ducklow HW (2013) Microzooplankton grazing along the Western Antarctic Peninsula. Aquat Microb Ecol 70:215-232.

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