PARALYTIC SHELLFISH POISONING IN SOUTHERN CHINA

The rapidly expanding mariculture and commercial region along the sout hern coast of China has experienced sporadic outbreaks of paralytic sh ellfish poisoning for nearly 30 years, yet virtually nothing is known of the nature of that toxicity or of the causative organisms. This stu dy presents the first direct comparisons of the high performance liqui d chromatography toxin composition profiles of shellfish implicated in paralytic shellfish poisoning outbreaks in Daya Bay with Alexandrium tamarense cultures established from those waters. The three cultures t hat were analyzed produced an unusually high proportion of the low pot ency N-sulfocarbamoyl toxins C1 and C2 (nearly 90% of the total), and only trace quantities of the other saxitoxin derivatives. Total toxici ty was thus very low with mild acid extraction, ranging between 7.2 an d 12.7 fmole cell(-1), or 0.7-0.9 pg saxitoxin equiv. cell(-1). Follow ing acid hydrolysis using the standard AOAC extraction method, the dom inant toxins in the cultures were gonyautoxins 2 and 3 and decarbamoyl gonyautoxins 2 and 3. Total potency increased fourfold to 2.6-3.4 pg saxitoxin equiv. cell(-1) following acid hydrolysis. These cultures ar e thus at the low end of the range of toxicities recorded for members of the A. tamarense species complex. Two scallop samples and one musse l sample collected from Daya Bay during paralytic shellfish poisoning episodes in 1990 and 1991 were also analyzed following the AOAC extrac tion procedure. The toxin profiles were similar for the three shellfis h samples, in that the same suite of toxins were present in each, but the relative proportion of those toxins varied. The dominant toxins we re gonyautoxins 2 and 3 and toxins C1-C4. Total toxicity was 336 and 6 54 mu g saxitoxin per 100 g meat for the scallop samples, and 723 for the mussels. Toxins C3,4 were present in the shellfish at up to 22 mol e%, but were not detected in cultures, even when mild acid was used fo r extraction. Despite the otherwise similar nature of the culture vers us the shellfish toxin signatures, the presence of C3,4 indicates that another strain or species of Alexandrium, or possibly a paralytic she llfish poisoning-producing species of another genus was responsible fo r the 1990 and 1991 paralytic shellfish poisoning outbreaks in Daya Ba y. Since the cultures analyzed were of low intrinsic toxicity, A. tama rense may be more widespread along the south coast of China than is su ggested by the sporadic pattern of past paralytic shellfish poisoning outbreaks. Blooms with high cell densities are required to generate su fficient toxin to be dangerous. The alarming increase in algal blooms in Chinese waters due to persistent and growing pollution may make the se low toxicity populations more problematic in the future. Copyright (C) 1996 Elsevier Science Ltd