Kazumi Matsuoka

Distribution of dinoflagellate cysts in surface sediments from the Yellow Sea and East China Sea

Abstract The distribution of dinoflagellate cysts in surface sediment samples of the Yellow Sea and East China Sea has been examined from 48 samples. Emphasis has been placed on ellipsoidal cysts of the genus Alexandrium. Results show two concurrent cyst distribution trends in latitudinal and longitudinal directions. In the latitudinal trend, cysts are most abundant north of 34°N in the Yellow Sea, where Spiniferites bulloideus (Deflandre et Cookson) Sarjeant, and ellipsoidal Alexandrium cysts generally dominate. Cyst concentration decreases towards both sides of the northern East China Sea in a longitudinal direction. Various factors such as cyst production, particle size of sediment and sedimentation rates may contribute to the dinoflagellate cyst distribution in the Yellow Sea and northern East China Sea. The protoperidinioid/gonyaulacoid (P/G) ratio, which is considered to increase in proportion with increasing primary production, is of limited use in comparing with other areas because its value remains high in both high and lower primary production areas in our study.

observations of the feeding behavior and growth rates of the heterotrophic dinoflagellate polykrikos kofoidii (polykrikaceae, Dinophyceae)

Abstract This paper describes the feeding behavior of the heterotrophic dinoflagellate Polykrikos kofoidii Chatton on Gymnodinium catenatum Graham. Polykrikos kofoidii used a nematocyst to pull the prey into its body through the posterior sulcus, finally engulfing the prey completely. We measured growth rates of P. kofoidii on diverse assemblages of dinoflagellate prey. Gymnodinium catenatum was one of the best food sources for P. kofoidii, supporting a rapid growth rate in excess of one doubling per day. This suggests that G. catenatum populations may be controlled by P. kofoidii predation in natural bloom conditions. However, P. kofoidii cannot be a potential bloom-controlling factor in all toxic dinoflagellate blooms because it is rapidly killed by at least three Alexandrium strains.

Holocene dinoflagellate cyst assemblages in shallow water sediments of the Tsushima Islands, west Japan

Abstract The paleoceanography of the eastern part of the East China Sea since ca. 10,000 yr BP is reconstructed based on Holocene dinoflagellate cyst assemblages obtained from cores collected at the west coast of the Tsushima Islands, west Japan. The dinoflagellate cyst assemblages in the core clearly show the coastal environment from the early Holocene transgression after the last glacial stage to the late Holocene regression through the climatic optimum in the middle Holocene.