Functional structure of microbial food web in the Senegal River Estuary (West Africa): impact of metazooplankton

on microbial plankton isolated from the Senegal River Estuary. Experiments performed in microcosms were based on size-class fractionation (3, 12, 20 and 60 m size classes) of the microbial community in order to obtain different assemblages, including bacteria, heterotrophic nanoflagellates (HNF), ciliates, pico- and nanophytoplankton. Removal of bacterial predators >3 m increased the net growth rate of heterotrophic bacteria from 0.437 day � 1 in the presence of all predators (fraction 12 m caused an increased net growth rate of flagellates from 0.102 day � 1 (fraction 12 m by this copepod, allowing an increase in HNF growth rates through indirect effect. The highest ingestion rate over 60 h of experiment was recorded for the copepod Temora (61.1 m 3 ngC � 1 h � 1 ) and the lowest value for barnacle larvae (25.6 m 3 ngC � 1 h � 1 ). An intermediate value (47.5m 3 ngC � 1 h � 1 )was recorded for thecopepodAcartia clausi.Alltheseingestion ratesweremainlychanneled in the size classes between