Protozoans are important consumers of prokaryotes, and are able to facilitate remineralization of detritus, thus playing a pivotal role in nutrient recycling (Sherr et al. 1982; Sherr and Sherr 1993; Patterson et al. 1989; Hondeveld et al. 1992). In addition, protozoans are consumed by meio-and macrofauna, providing a trophic link between prokaryotes and the upper trophic levels of the food webs (Sherr et al. 1986a). Direct estimates of bacteria losses by grazing can provide an estimate of the carbon being transferred to higher trophic levels (Carrick et al. 1991; Dolan and Gallegos 1991). Also, virus-protozoa interactions may be important in the material ow in aquatic systems. Phagotrophic nanoagellates consume and digest, either directly or indirectly (via ingestion of virus-infected bacteria), a variety of marine viruses, thereby deriving nutritional benet and serving as a natural sink for marine viral particles (González and Suttle 1993; Maranger et al. 2002). Information on viruses-prokaryotes-protozoans interactions in benthic environments and the biomass ow in the sediment are almost completely lacking (Fischer et al. 2003; Wieltschnig et al. 2003). The reasons for the general lack of benthic studies are the specic characteristics of the sediment, presenting several problems including the difculty of quantitative extraction of the organisms from sediment.