MEPS 411:101-115 (2010)  -  doi:10.3354/meps08646

Role of ciliates and other microzooplankton in the Irminger Sea (NW Atlantic Ocean)

David J. S. Montagnes1,*, John Allen2, Louise Brown2,5, Celia Bulit3, Russell Davidson2, Sophie Fielding2, Mike Heath4, N. Penny Holliday2, Jens Rasmussen4, Richard Sanders2, Joanna J. Waniek2,6, David Wilson1

1School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK
2National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK
3Departamento El Hombre y su Ambiente, Universidad Autónoma Metropolitana-Xochimilco, Calzada del Hueso 1100,
04960 México DF, Mexico
4Marine Scotland Science, PO Box 101, 375 Victoria Road, Aberdeen AB11 9BD, UK
5Present address: School of Geography and Geosciences, University of St Andrews, Irvine Building, St Andrews, Fife KY16 9AL, UK
6Present address: Leibniz-Institut für Ostseeforschung Warnemüde 15, 18119 Rostock, Germany

ABSTRACT: This study focuses on a large region of the open ocean where we predict that microzooplankton significantly influence foodweb structure over much of the year. The Irminger Sea exhibits low primary production that is generally poor for copepod production; in such waters, ciliates and other microzooplankton are major grazers of primary production and contribute significantly to the diets of holo- and mero-mesozooplankton. Surface plankton samples were collected during an extensive survey across the basin and along one transect at several depths, over 3 seasons (winter, spring, summer), but not including the spring bloom. Microzooplankton and phytoplankton samples were fixed with Lugol’s solution and microscopically enumerated for species abundance; biomass was determined from cell volumes. Basin-scale distributions of abundance, biomass, and production were examined by geostatistical and multidimensional scaling methods. Dominance of the <10 µm phytoplankton suggests that this should be a microzooplankton-dominated food web. Ciliates and heterotrophic dinoflagellates are abundant in terms of numbers and biomass; heterotrophic dinoflagellates are more abundant than ciliates, but are less dominant in terms of biomass. Using ciliates as a proxy for all microzooplankton, we suggest that there are seasonal patterns in occurrence, and there is no basin-scale patchiness related to hydrographic features. We suggest that ciliate production is sufficient to account for the removal of 15 to 30% of the <10 µm primary production. If heterotrophic dinoflagellates were included in these estimates, removal may be doubled (i.e. 30 to 60%). We therefore contend that microzooplankton are major phytoplankton consumers in the system and should be carefully parameterised in models of this region.

KEY WORDS: Ciliates · Biomass · Food web · Nanoplankton · Picoplankton · Phytoplankton

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Cite this article as: Montagnes DJS, Allen J, Brown L, Bulit C and others (2010) Role of ciliates and other microzooplankton in the Irminger Sea (NW Atlantic Ocean). Mar Ecol Prog Ser 411:101-115

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