Spreading Mechanism of Harmful Red Tides in WESTPAC Area

日本和西太平洋国家，特别是东南亚的科学家进行了合作研究，以澄清造成鱼类和贝类毒素污染的有毒浮游生物的分布现状，重点是阐明其地理扩张的机制。研究结果表明，麻痹性贝毒（PSP）的致病菌为巴哈马甲藻（Pyrodinium bahamense）、链状裸甲藻（Gymatinium catenatum）和亚历山大藻（Alexandrum spp.）。广泛分布于热带沃茨。在热带沃茨中还发现了两种可能导致中毒的甲藻，尾甲藻和迈尔斯甲藻。一种引起失忆症中毒的硅藻（ASP）。也广泛分布，但尚未证实有任何毒素污染。这些有毒物种的分布范围随着研究的深入而不断扩大，但目前尚不清楚它们是最近从其他地方入侵的，还是在同一地区长期停留的。在世界上PSP危害最严重的菲律宾，巴哈马对虾的分布范围正在向南扩展至棉兰老岛。在马来西亚沙巴发现了相同的物种，那里的水流来自棉兰老岛。在菲律宾沃茨也发现了其他PSP物种，G.catenatum和Alexandrum sp.。在本研究之前一直否认有毒浮游生物存在的越南，在沿海沃茨和对虾养殖池塘中发现了4种亚历山大藻（A.andersonii，A.insuetwn，A.minutum，A.tamiyavanichii）。使用单藻培养物证实了微小曲霉的PSP毒素生产力。从对虾养殖池分离的底栖硅藻Nitzschia sp中发现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.