Ref ID : 6695
Hera Karayanni, Urania Christaki, France Van Wambeke, Melilotus Thyssen, and Michel Denis; Heterotrophic nanoflagellate and ciliate bacterivorous activity and growth in the northeast Atlantic Ocean: a seasonal mesoscale study. Aquatic Microbial Ecology 51:169-181, 2008
Reprint
In File
Notes
The grazing effect of the heterotrophic nanoflagellates (HNF) and ciliates on bacterial production (BP), as well as their growth rates, was studied in winter, spring and autumn 2001 during the French research project Programme Ocean Multidisciplinaire Meso-Echelle (POMME) in the northeast Atlantic Ocean (38 to 45 degrees N, 16 to 22 degrees W). The variability of different parameters studied appears to be largely controlled by the seasonal and latitudinal gradients of primary production rather than the strong eddy activity at the mesoscale level in the area. Heterotrophic microbial abundance, biomass and protistan grazing varied temporally, presenting highest values during the phytoplankton bloom, during the spring period and following the northward propagation of the bloom. HNF biomass integrated over the upper 100 m was highest in spring (270 to 850 mgC m-2). Ciliate integrated biomass was generally < /_160 mgC m-2 except in a Tintinnus sp. bloom in a northern anticyclonic eddy (A1) in spring when it reached 637 mgC m-2, HNF and ciliate growth rates varied from 0.2 to 0.7 day-1 and 0.2 to 1.4 day-1 respectively. The fraction of BP consumed by ciliates was generally <10% except in the anticyclonic eddy A1 in spring during a tintinnid bloom when it reached 37% of BP. In conclusion, our data revealed that HNF can remove a large fraction of bacterial production in the northeast Atlantic Ocean (83+/-27%, average of all sampling sites and seasons). Ciliates transferred less carbon to higher trophic levels than did HNF; however, episodic high occurrence of large baterivorous ciliates, primarily tintinnids, increased the role of these organisms as C-links in the microbial food web.