Toxic Diatoms Belonging to the Genus Pseudo-nitzschia from the Coast of Southern China

Only two species of potentially toxic diatoms have been observed in the waters of southern coastal China, Pseudo-nitzschia multiseries Hasle and P. pseudodelicatissima (Hasle) Hasle. Pseudo-nitzschia multiseries was first described for coastal China by Dickman (1996) and P. pseudodelicatissima from coastal China is described here for the first time. In addition to these two potentially toxic species, five non-toxic species of Pseudo-nitzschia were observed (P. subpacifica, P. pungens, P. seriata, P. Sinica and P. multistriata). P. sinica is a new species (Qi et al. 1994) and P. subpacifica and P. multistriata were observed for the first time in southern China by Qi and Zheng (unpublished data). P. pungens was observed at all stations surveyed along the entire southern-central coast of China. It was present most of the year except for late winter. In June of 1990 a bloom of Pseudo-nitzschia species (140,000 cells L-1) was observed in Mirs Bay (Tai Pang Wan). This was the highest Pseudo-nitzschia density reported for the coastal waters of southern China. The highest density of Pseudo-nitzschia in Hong Kong, occurred in September of 1996 (109,000 cells L-1). Because identification of the different species of Pseudo-nitzschia necessitates the use of a scanning electron microscope (SEM) the ratio of potentially toxic to non-toxic species was inferred from SEM. The ratio ranged from 74-100 non-toxic for every potentially toxic species identified under the SEM.