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Aquatic Microbial Ecology

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AME 40:293-298 (2005)  -  doi:10.3354/ame040293

Heterotrophic dinoflagellate fecal pellet production: grazing of large, chain-forming diatoms during upwelling events in Monterey Bay, California

K. R. Buck*, R. Marin III, F. P. Chavez

Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, USA

ABSTRACT: An athecate phagotrophic dinoflagellate (Gyrodinium sp.) ingests chain-forming diatoms that are abundant during upwelling events in Monterey Bay, CA, USA, and contiguous waters. The chains are digested and egested with a peritrophic membrane covering the fecal pellet, consistent with earlier reports from high productivity environments. The maximum abundance of the dinoflagellate during more than a decade of monitoring was 4000 cells l–1. Its primary prey comprised chains of centric diatoms such as Chaetoceros spp. or Skeletonema spp., although Pseudo-nitzschia spp. were also observed in the dinoflagellate‘s fecal pellets. Maximum grazing by this dinoflagellate represented 10% of the total phytoplankton biomass. Our observations suggest a lesser role of large heterotrophic dinoflagellates in the ecology of central California waters compared to other regions.

KEY WORDS: Heterotrophic dinoflagellates · Microzooplankton grazing

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