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Aquatic Microbial Ecology

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AME 67:47-58 (2012)  -  DOI:

The taste of diatoms: the role of diatom growth phase characteristics and associated bacteria for benthic copepod grazing

Marleen De Troch1,*, Inge Vergaerde1,3, Clio Cnudde1, Pieter Vanormelingen2, Wim Vyverman2, Magda Vincx1

1Marine Biology and 2Protistology and Aquatic Ecology, Biology Department, Ghent University, Campus Sterre, Krijgslaan 281 − S8,
Ghent 9000, Belgium
3University College West-Flanders, Rijselstraat 5, Brugge 8200, Belgium

ABSTRACT: The interactions between primary producers and their consumers are of particular interest for the overall functioning of marine ecosystems. The biochemical composition of the organisms involved affects the efficiency of energy transfer in marine food webs. In addition to top-down control by grazers, bottom-up control of these interactions by primary producers and associated bacteria has recently received more attention. Planktonic copepods selectively feed on older diatom cells, a behaviour regulated by changes in exometabolites around diatoms. To test whether this also applies to benthic copepods, Seminavis robusta cells in lag, exponential and stationary growth phases were biochemically screened, and the diversity of associated bacteria was assessed. The diatoms were subsequently 13C prelabelled and offered to the harpacticoid copepod Microarthridion littorale in a grazing experiment. Harpacticoid copepods incorporated more carbon from younger diatom cells in the lag growth phase, which might be based on (1) biochemical differences of diatom cells in different growth phases and (2) the bacteria associated with the diatoms. The younger diatom cells were characterised by a higher C:N ratio and more extracellular polymer secretions but a lower fatty acid content. The bacterial community on these cells differed from those on cells in the later growth phases. Our results thus suggest that the feeding strategies of benthic harpacticoid copepods differ from those of calanoid copepods. This outcome can be explained by the tight contact between benthic copepods and the typical carbon and bacteria-rich biofilm on sediments.

KEY WORDS: Diatoms · Grazing · Harpacticoid copepods

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Cite this article as: De Troch M, Vergaerde I, Cnudde C, Vanormelingen P, Vyverman W, Vincx M (2012) The taste of diatoms: the role of diatom growth phase characteristics and associated bacteria for benthic copepod grazing. Aquat Microb Ecol 67:47-58.

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