Succession of primary producers and micrograzers in a coastal ecosystem dominated by Phaeocystis globosa blooms
Résumé
The community structures and succession of phytoplankton, protozooplankton and copepods were studied from February 2007 to July 2009 in a coastal area of the eastern English Channel subject to Phaeocystis globosa blooms. While diatoms blooms preceded P. globosa blooms each year, the community structure and stock of heterotrophic protists appeared to be related to the dominant P. globosa life cycle stages. In 2007 the dominance of large colonies (>100 µm, 375 µg C L-1) which produced high biomass of healthy free cells (163 µg C L-1) accompanied high spirotrich ciliate stocks (up to 58 µg C L-1) and high abundances of the copepods Acartia clausi and Temora longicornis (up to 11 ind L-1). In 2008, the bloom which lasted a shorter period of time, was dominated by large colonies (328 µg C L-1), and fewer free cells (131 µg C L-1). This corresponded with a lower abundance of grazers, with stocks 1.6 times and 2.2 times lower of heterotrophic protist and copepods, respectively. In 2009, P. globosa bloom was again dominated by large colonies and <100 µm diatoms. This corresponded to a dominance of heterotrophic dinoflagellates among the protists (62% of the total heterotrophic protist biomass) and Acartia clausi (55% of the copepod abundance). Overall, heterotrophic dinoflagellates appeared to be likely the most important group of phytoplankton grazers.
Domaines
Océanographie
Origine : Fichiers produits par l'(les) auteur(s)