Temporal changes in the ciliate assemblage and consecutive estimates of their grazing effect during the course of a Heterocapsa circularisquama bloom |
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Authors: | Kamiyama Takashi; Matsuyama Yukihiko |
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Institution: | 1 Tohoku National Fisheries Research Institute, Fisheries Research Agency, Shinhama, Shiogama, Miyagi 985-0001, Japan and 2 National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Maruishi, Ohno, Saeki, Hiroshima 739-0452, Japan |
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Abstract: | Temporal changes in ciliate assemblages during the course ofa bloom of the harmful microalga Heterocapsa circularisquama(Dinophyceae) were investigated and consecutive estimates ofspecies-specific maximum grazing losses were analyzed from Augustto September 1998 at a site in western Hiroshima Bay, the SetoInland Sea of Japan. Temporal increases of the H. circularisquamamean concentration in the water column were observed twice (2529August and 710 September) with the maximum concentration(ca. 4000 cells mL1) being recorded on 25 August. Themain ciliate genera during the bloom were Favella, Tontonia,Eutintinnus, Tintinnopsis and Amphorellopsis. Increases of Favellaand Tontonia were observed when the concentration of H. circularisquamaranged from 260 to 1170 cells mL1. Total maximum grazingloss estimated from the abundance and ingestion rate of eachciliate species on H. circularisquama ranged from 1 to 75% standingstock removed d1 of the H. circularisquama concentration.High grazing losses mainly due to the genera Favella and Tontoniaoccurred during the period when the H. circularisquama concentrationwas decreasing. These results suggest that grazing by ciliateassemblages can influence the population dynamics of H. circularisquamadespite the potentially toxic nature of the phytoplankter. |
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