SHORT COMMUNICATION Particle retention efficiency of salps

Abstract. Five species of salps retained plastic beads a2.5 (im diameter with high (a60%) efficiency, while 1.0 p.m beads were retained with low (£15%) efficiency in all but one experiment. Salps feed as they swim by passing water through a pharyngeal mucous net and filtering out particles. Although they have been categorized as non-selective (Madin, 1974; Silver, 1975), the range of food they consume is limited on the small end by the size of particles which are retained by the mucous net. As more studies document the importance of small cells as primary producers in the open ocean, it is critical to identify the major consumers of this food source. Salps are widely distributed in oceanic waters (Kashkina, 1978) and salp swarms of high densities have been observed in various locations (e.g. Berner, 1957; Wiebe et al., 1979; Bathmann, 1988; Morris et al., 1988). In order to assess the importance of salps as grazers, it is necessary to quantify both the rate of feeding and the efficiency with which particles of various sizes are retained by different species. Although microscopic studies of salp feces have shown the presence of bacteria-sized particles (Silver and Bruland, 1981; Caron et al., 1989), th