Horizontal And Vertical Distribution Of Dinoflagellate Cysts From China Sea

The sediments in different depth were collected from China seas which embraces 30 sites from Bohai Bay,10 sites from Changjiang River Estuary and 6 sites from Taiwan Strait during 2004 to 2005 to investigate the species composition, horizontal and vertical distribution of dinoflagellates cysts from Chinese coasts. Thirty species of dinoflagellates cysts were identified in the sediments based on morphological features of the cyst, whereas 5 types of them were unidentified. Heterotrophic dinoflagellates cysts dominated in the cyst assemblages from three different areas of China Sea. Two Paralytic Shellfish Poisoning (PSP) producing toxic species, Alexandrium tamarense (Lebour) Balech and Gymnodinium catenatum Graham were found in all sampling sites of Bohai Bay, Changjiang River Estuary and Taiwan Strait, which distributed with a large range but low concentration. The species composition and concentrate distribution of dinoflagellates cysts from China Sea had increasing current from north to south. There are 22 types of cysts were detected in Bohai Bay with the average concentration of 163 cysts/g DWt. There are 24 types in Changjiang River Estuary with the average concentration of 398 cysts/g DWt and 30 types in Taiwan Strait highest, with the average concentration of 817 cysts/g DWt. The value of Shannon-Weiner diversity index (H') from Bohai Bay varied between 1.18～3.20, Changjiang River Estuary varied between 2.57～3.27 and 1.93752～ 3.65758 from Taiwan Strait. Results of vertical distribution of dinoflagellate cysts indicated that total cysts' composition, concentration and the range of diversity index in different depth of sediment layers from each sea were different. The concentration of dinoflagellate cysts in different depth from Bohai Bay ranged from 136～202 cysts/g DWt with the diversity index varied between 2.78~2.88. The concentration of dinoflagellate cysts from Changjiang River Estuary ranged from 351 cysts/g DWt～432cysts/g DWt with the diversity index varied between 2.57～3.27. The data of concentration from Taiwan Strait were 926 cysts/g DWt～626 cysts/g DWt and 2.6097～3.0110. To a large extent the concentration of cysts negatively correlated with the diversity index in most of the samples collected.