Impact of copepod grazing on developmental dynamics of an iron-induced phytoplankton bloom (EisenEx)


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jhenjes [ at ] awi-bremerhaven.de

Abstract

Dynamics of metazooplankton populations and the impact of grazing on their potential food supply was studied in an in situ iron fertilization experiment (EisenEx) in the Antarctic Circumpolar Current. Copepod nauplii, copepodites and the adults of small copepods (< 1.5 mm) were sampled with Niskin bottles (12 L). The exceptionally high concentrations we recorded (average 42 nauplii L-1 and 24 copepodites and adults L-1) suggest that vertical net hauls seriously undersample these organisms. During the experiment copepod nauplii numbers stayed more or less constant. Abundances of copepodites and adults of small copepods increased threefold indicating either enhanced recruitment from naupliar and copepodite stages respectively, and/or congregation within the patch due to migration of individuals from below the mixed layer. In either case the copepod population appeared to be food-limited outside the patch. Copepod grazing apparently suppressed protozooplankton stocks: Heterotrophic dinoflagellates and aloricate ciliates increased with food supply but decreased subsequently. Tintinnids decreased but empty loricae increased twofold indicating heavy grazing mortality. Thus interactions between grazer populations facilitated population growth of diatoms which dominated the iron-induced diatom bloom.



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Conference (Talk)
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Not peer-reviewed
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Published
Event Details
SS11: Biodiversity, Biogeochemistry and Trophic Interactions: The Braid of Pelagic Microbial Ecology, American Society of Limnology and Oceanography (ASLO) Summer Meeting 2005,1924 June, Santiago de Compostela, Spain.
Eprint ID
13506
Cite as
Henjes, J. , Assmy, P. , Klaas, C. and Smetacek, V. (2005): Impact of copepod grazing on developmental dynamics of an iron-induced phytoplankton bloom (EisenEx) , SS11: Biodiversity, Biogeochemistry and Trophic Interactions: The Braid of Pelagic Microbial Ecology, American Society of Limnology and Oceanography (ASLO) Summer Meeting 2005,1924 June, Santiago de Compostela, Spain .


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