Zooplankton feeding ecology: clearance and ingestion rates of the salps Thalia democratica, Cyclosalpa affinis and Salpa cylindrica on naturally occurring particles in the Mid-Atlantic Bight

Aggregate stages of the salps Thalia democratica, Cyclosalpa affinis and Salpa cylindrica collected by SCUBA diving in the Mid-Atlantic Bight were fed with naturally occurring food assemblages. This is one of the few studies where salps have been fed with natural food assemblages. The estimated clearance rate for all species based on disappearance of chlorophyll varied from 82 to 444 mL individual -1 day -1 . Cell counts showed that T. democratica mostly ingested carbon from autotrophic nanoflagellates and autotrophic dinoflagellates. Ingestion by S. cylindrica was primarily on larger prey, such as dinoflagellates, while C. affinis ingested auto- and heterotrophic nanoflagellates. All main prey types ingested by salps corresponded to those that contributed most to biomass at each experimental station. Thus, salps fed on naturally occurring particles primarily in proportion to prey biomass and to their mechanical capacity to be retained and ingested. Feeding by salps on dinoflagellates and ciliates implies that they may act not only as potential competitors with microzooplankton, but also as consumers of them.