Spreading Mechanism of Harmful Red Tides in WESTPAC Area

日本与西太平洋国家，特别是东南亚的科学家开展了合作研究，阐明了造成鱼类和贝类毒素污染的有毒浮游生物的分布现状，重点阐明了其地理扩张的机制。研究结果表明，导致麻痹性贝类中毒（PSP）的病原菌bahamense、Gymnodinium catenatum和Alexandrium spp.广泛存在于热带水域。两种可能导致腹泻中毒的鞭毛藻，尾鞭毛藻和d.m miles在热带水域也很常见。引起健忘症中毒（ASP）的一种硅藻（pseudonitzschia spp.）也广泛分布，但尚未证实是否有毒素污染。随着研究范围的扩大，这些有毒物种的分布范围似乎越来越广，但目前尚不清楚这些物种是最近从其他地方入侵还是长期停留在同一地区。在世界上受PSP危害最严重的菲律宾，p.b hamense的分布正在向南扩展至棉兰老岛。在水流从棉兰老岛流入的马来西亚沙巴也发现了同样的物种。在菲律宾水域也发现了其他种类的斑虫，G.catenatum和Alexandrium sp.。利用在班乃岛采集的浮游生物样本，首次在热带鞭毛藻中证实了尾尾藻和尾尾藻的DSP毒素产量。在本研究之前不承认有毒浮游生物存在的越南，在沿海水域和养虾池中发现了四种亚历山大菌（A.andersonii， A.insuetwn， A.minutum， A.tamiyavanichii）。用单菌培养法证实了小黄芽孢杆菌的产毒能力。从对虾养殖池分离的底栖硅藻（Nitzschia sp）中发现了ASP毒性。

Cooperative research among scientists in Japan and western Pacific countries, especially Southeast Asia, was conducted in order to clarify the current situation of distribution of toxic plankton, which caused toxin contamination in fish and shellfish, with emphasis on elucidation of mechanism of their geographical expansion. The research result revealed that causative organisms responsible for paralytic shellfish poisoning (PSP), Pyrodinium bahamense, Gymnodinium catenatum, and Alexandrium spp. occurred widely in tropical waters. Two dinoflagellates possibly responsible for diarrhetic poisoning (DSP), Dinophysis caudata and D.miles were also found commonly in tropical waters. A diatoms responsible for amnesic poisoning (ASP) Pseudo-nitzschia spp. were also distributed widely, but any toxin contamination had not been confirmed yet. Distribution of these toxic species looks wider and wider, as research was conducted in new area, although it was not clear whether the species invaded from other place recently or stayed the same area for a long time.In the Philippines, where damage caused by PSP is most serious in the world, the distribution of P.bahamense was expanding to south to Mindanao Island. The same species was found in Saba, Malaysia where water current reach from Mindanao. Other PSP species, G.catenatum and Alexandrium sp. were also found in the Philippine waters. Using plankton samples collected from Panay Island, DSP toxin productivity of D.caudata and D.miles was confirmed for the first time in tropical dinoflagellates.In Vietnam, where the occurrence of toxic plankton was denied before the present research, four Alexandrium species (A.andersonii, A.insuetwn, A.minutum, A.tamiyavanichii) were found in coastal waters and shrimp culture ponds. PSP toxin productivity of A.minutum was confirmed using an unialgal culture. ASP toxicity was found in benthic diatom, Nitzschia sp, isolated from shrimp culture pond.