Relationship between the number of cysts that germinate and the occurrence of red tides in the inner part of the Ariake Sea

Abstract

In recent years, Chattonella has frequently caused red tides in the inner part of the Ariake Sea. However, information on the cyst in the sea is currently limited. In the present study, cyst germination of Chattonella was investigated from 2011 to 2013 at 10 stations. Development of vegetative cells of Chattonella was also monitored at 6 stations. The numbers of germinated cysts ranged between 1.38±1.38 and 3.71±2.33 cysts cm^-2. The number was low in 2012 when no Chattonella bloom had occurred the previous summer. Although cyst germination was low at station S3, vegetative cells of Chattonella were detected first at that station in 2012 and 2013. At S3, the number of vegetative cells was also high as compared to the 6 stations investigated; hence, population development of Chattonella vegetative cells may not necessarily occur at the station where the cysts germinated. Moreover, in addition to maturation, cyst survival is considered an important process for germination the following spring.