Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

2013

Journal

Aquatic Microbial Ecology

Volume

70

Issue

3

First Page

215

Last Page

232

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 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.

DOI

10.3354/ame01655

Keywords

Protozooplankton Community Structure; Microbial Food-Web; Southern-Ocean; Phytoplankton Growth; Ciliate Microzooplankton; Heterotrophic Protists; Bacterial Production; Atlantic Sector; Coastal Waters; Austral Summer

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