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Aquatic Microbial Ecology

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AME 17:91-98 (1999)  -  doi:10.3354/ame017091

Grazing impacts of the heterotrophic dinoflagellate Polykrikos kofoidii on a bloom of Gymnodinium catenatum

Yukihiko Matsuyama1,*, Masahide Miyamoto2, Yuichi Kotani1

1National Research Institute of Fisheries and Environment of Inland Sea, Maruishi, Ohno, Saeki, Hiroshima 739-0452, Japan
2Kumamoto Ariake Fisheries Direction Office, Iwasaki, Tamana, Kumamoto 865-0016, Japan

ABSTRACT: In 1998, a red tide of the paralytic shellfish poisoning (PSP)-producing dinoflagellate Gymnodinium catenatum Graham occurred in Yatsushiro Sea, western Japan. The dramatic decline of dominant G. catenatum cells occurred during the field and laboratory assessments, accompanied with growth of the heterotrophic dinoflagellate Polykrikos kofoidii Chatton. Microscopic observations on both field and laboratory cultured bloom water revealed that >50% of P. kofoidii predated on the natural population of G. catenatum, and 1 to 8 G. catenatum cells were found in food vacuoles of P. kofoidii pseudocolonies. Our results suggest that predation by P. kofoidii contributes to the cessation of a G. catenatum bloom.

KEY WORDS: PSP · Gymnodinium catenatum · Polykrikos kofoidii · Harmful algal bloom · Predation · Heterotrophic dinoflagellate

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