Experimental evaluation of herbivory in the ctenophore Mnemiopsis leidyi relevant to ctenophore-zooplankton-phytoplankton interactions in Narragansett Bay, Rhode Island, USA

Publisher Website
Google Scholar
Abstract
Herbivory of Mnemiopsis leidyi and its interactions with phytoplankton and non-gelatinous zooplankton were examined in small-scale microcosm experiments. Clearance rates for M. leidyi incubated with phytoplankton were generally negative, but ranged up to 4.5 1 ctenophore−1 day−1 when the large (80 μm ø) diatom Ditylum brightwelli was offered as a food source. These highest ingestion rates would provide Mnemiopsis with only 21 % of its daily carbon requirements for respiration. Mean shrinkage of M. leidyi was 8.2–51% when incubated with phytoplankton. Although M. leidyi neither fed actively on phytoplankton, nor satisfied its nutritional needs on such a diet, the chain-forming diatom Skeletonema costatum became entangled in mucus strands and balls produced by M. leidyi in the absence of zooplankton. Attachment onto mucus occurred at phytoplankton concentrations commonly observed in Narragansett Bay and may be important in the formation of “marine snow” during summer M. leidyi pulses; phytoplankton sinking rate and the “package size” available to herbivores would also be affected. The experiments support our previous hypothesis based on field observations in Narragansett Bay that M. leidyi indirectly regulates phytoplankton abundance there during the summer bloom as a consequence of predation on zooplankton. The extent to which M. leidyi influenced phytoplankton dynamics in the microcosms was dependent on the relative abundance and physiological state of the three trophic levels. A food web diagram for M. leidyi is presented.

This publication has 0 references indexed in Scilit: