Medusa Predation and Plankton Dynamics in a Temperate Fjord, British Columbia

Publisher Website
Google Scholar
Abstract
A second spring bloom, dominated by the diatoms Skeletonema costatum and Chaetoceros spp., has been repeatedly observed in a temperate fjord on southern Vancouver Island, B.C. Ammonia, possibly regenerated by herbivorous zooplankton, formed the principal nitrogen supply for the second spring bloom. High production of phytoplankton and zooplankton during the first spring bloom resulted in plentiful food for polyps of the leptomedusa, Phialidium gregarium, which then produced a large quantity of medusae (> 110 mg dry weight∙m−3). Medusa predation on zooplankton reduced herbivore grazing pressure, thus permitting development of the second spring bloom. Continuing predation by P. gregarium reduced the prey population to such an extent that medusa standing stock declined to 5% of its maximum value. The second spring bloom probably ended due to nitrogen limitation, and when medusa biomass declined herbivore and ammonia concentrations began to rise. Results indicate that the release of herbivore grazing pressure due to predation can stimulate phytoplankton growth. Key words: phytoplankton ecology, phytoplankton physiology, zooplankton grazing, zooplankton predation, Phialidium gregarium, Skeletonema costatum

This publication has 0 references indexed in Scilit: