@article {Guillou2001, title = {Grazing impact of two small heterotrophic flagellates on Prochlorococcus and Synechococcus}, journal = {Aquatic Microbial Ecology}, volume = {26}, number = {2}, year = {2001}, note = {tex.mendeley-tags: 2001,rcc,sbr?hyto}, pages = {201{\textendash}207}, abstract = {In open oceanic waters, phytoplankton biomass is dominated by organisms below 2 to 3 mum in size (pico- and small nanophytoplankton). The cell concentration of these populations is very stable in time and space as a consequence of nutrient limitation and strong grazing pressure, Although the identity of the organisms that directly graze on picoplankton is largely unknown, they are thought to be very small, i.e. {\textexclamdown}3 to 5 {\textexclamdown}mu{\textquestiondown}m, Here, we analyze the grazing impact of 2 small flagellates, Symbiomonas scintillans and Picophagus flagellatus, upon 2 oceanic cyanobacteria, Prochlorococcus and Synechococcus. S. scintillans does not feed on the 2 cyanobacteria. In contrast, P. flagellatus appears as an active predator capable of drastically reducing prey concentrations. The flagellate displays a substantial division rate of the order of 2 doublings d(-1) when fed on Prochlorococcus cells, but no significant growth is recorded when Synechococcus is used as prey. As the majority ({\textquestiondown} 80\%) of P. flagellatus cells can pass throughout a 2 mum filter, the impact of such tiny predators should be taken into consideration during field experiments that rely on size fractionation to separate grazers from prey.}, keywords = {2001, Algal Class, Equatorial Pacific, Growth Rates, Laboratory Cultures, Marine, Nanoplankton, PICODIV, picoplankton, Prey, rcc, SBR$_\textrmP$hyto, sbr?hyto, Size, Sp Nov}, doi = {10.3354/ame026201}, author = {Guillou, L and Jacquet, S and Chr{\'e}tiennot-Dinet, M.-J. and Vaulot, D} }