AME 45:163-170 (2006)  -  doi:10.3354/ame045163

Grazing and growth of the heterotrophic flagellate Diphylleia rotans on the cyanobacterium Microcystis aeruginosa

Bo-Ra Kim1, Shin-ichi Nakano2, Baik-Ho Kim1, Myung-Soo Han1,*

1Department of Life Science, Hanyang University, Seoul 133-791, Korea 2 LAFWEDY, Faculty of Agriculture, Ehime University, Tarumi 3-5-7, Matsuyama, Ehime 790-8566, Japan

ABSTRACT: The grazing and growth rates of the algivorous heterotrophic flagellate (HF) Diphylleia rotans were investigated on toxic (Microcystis aeruginosa NIER-10001, M. aeruginosa NIES-298, M. viridis NIES-102 and M. wesenbergii NIES-104) and non-toxic (M. aeruginosa NIES-101) Microcystis strains as well as other different algae such as the green alga ChlorellaTM (Aquanet), and diatoms Cyclotella meneghiniana and Stephanodiscus hantzschii. The flagellate D. rotans showed active growth when fed M. aeruginosa and lower levels of growth when fed ChlorellaTM, but no growth when fed C. meneghiniana and S. hantzschii. The flagellate grew actively at 25°C and at a pH range between 6 and 9. The highest maximum specific growth rate (1.88 d–1) and a high ingestion rate (27.0 prey HF–1 d–1) by D. rotans were observed when they were fed the most toxic of the 5 Microcystis strains, M. aeruginosa NIER-10001. These results suggest that D. rotans has a high tolerance to M. aeruginosa and may undergo microcystin-mediated growth.

KEY WORDS: Algivores · Heterotrophic flagellates · Diphylleia rotans · Microcystis spp. · Microcystin-mediated growth · Ingestion

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