SPECIES-SPECIFIC GROWTH PERFORMANCE AND GRAZING MORTALITY OF THE DIATOM ASSEMBLAGE DURING AN IN SITU IRON-INDUCED BLOOM IN THE SOUTHERN OCEAN (EISENEX)


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passmy [ at ] awi-bremerhaven.de

Abstract

Phytoplankton blooms play a major role in global elemental cycles and marine food chains but different species impact these in different ways. Hence a mechanistic understanding of the factors regulating species dominance is a prerequisite to predictive modelling. Results from EisenEx revealed 6 distinct response behaviours to iron fertilization. Five species of the over 50 recorded, contributed 48% of total diatom biomass. Of these, two species (a pennate and a centric) reacted immediately with accumulation rates about double those of other species and built up population size exponentially. In contrast species with initially highest abundances responded after a week with a brief period of rapid accumulation which levelled off later. The ratio of live cells to intact empty and broken frustules (LC:EBF), used as a measure of mortality, increased steadily inside the fertilized patch indicating that the grazer assemblage could not keep pace with growth of the dominant species. Species-specific differences in the LC:EBF ratio and the ratio of intact empty to broken frustules indicated that selective grazing by proto- and metazooplankton played an important role in structuring the diatom assemblage.



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Published
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ASLO Summer Meeting 2005, Special Session 11: Biodiversity, biogeochemistry and trophic interactions: The braid of pelagic microbial ecology. 19.-24. June, Santiago de Compostela, Spain..
Eprint ID
13505
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Assmy, P. , Henjes, J. , Klaas, C. and Smetacek, V. (2005): SPECIES-SPECIFIC GROWTH PERFORMANCE AND GRAZING MORTALITY OF THE DIATOM ASSEMBLAGE DURING AN IN SITU IRON-INDUCED BLOOM IN THE SOUTHERN OCEAN (EISENEX) , ASLO Summer Meeting 2005, Special Session 11: Biodiversity, biogeochemistry and trophic interactions: The braid of pelagic microbial ecology. 19.-24. June, Santiago de Compostela, Spain. .


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