In situ germination patterns of cysts, and bloom formation of some armored dinoflagellates in Onagawa Bay, north-east Japan

Abstract

The relationship in seasonality between in situ germination phenomena and the occurrence of vegetative populations was investigated for three photosynthetic and three heterotrophic dinoflagellate species inhabiting Onagawa Bay, north-east Japan. Two different types of germination pattern of the cyst populations on the surface sediment were recognized for the six species, i.e. 'sporadic' and 'synchronous'. In the latter, three subtypes were identified as warm-water type, cold-water type and intermediate type, according to their seasonality. Cysts play an important role as seeds of the vegetative populations in all the species. However, bloom is performed in a species-specific manner under seasonally fluctuating environmental conditions. The bay fosters many cyst-forming dinoflagellates, which perform seasonal succession of the vegetative populations, as a whole.