Microzooplankton community associated with phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean)
Résumé
The spatial and temporal community composition of microzooplankton (dinoflagellates and ciliates) was assessed in the
Kerguelen area (Southern Ocean) during the KEOPS2 cruise in early spring (October–November) 2011. This naturally
iron-fertilized region was characterized by a complex mesoscale circulation resulting in a patchy distribution of
phytoplankton blooms. Collectively, 97 morphospecies of dinoflagellates and ciliates belonging to 41 genera were identified
by microscopy, and 202 Alveolata-related OTUs (operational taxonomical units) were retrieved with tag-pyrosequencing.
Microscopy and pyrosequencing data were in accordance, in that diatom-consuming dinoflagellates were the most
enhanced taxa in the blooms. Dinoflagellates also showed significant positive relationships with phytoplankton pigments,
while no major differences were found in the ciliate abundances inside and outside the blooms. Cluster analysis showed
clear differences in the phytoplankton and microzooplankton community structures between the iron-fertilized and HNLC
(high nutrient low chlorophyll) waters, and between the blooms, concerning their location and the fertilization
mechanisms. These results were combined with the rates of primary production and mesozooplankton consumption
determined for the study area. The potential role of dinoflagellates and ciliates as phytoplankton consumers and as prey for
mesozooplankton was then evaluated. Overall, heterotrophic dinoflagellates were probably the most important group of
phytoplankton grazers, and a potential food source for copepods.
Domaines
OcéanographieOrigine | Fichiers produits par l'(les) auteur(s) |
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