Studies on Red Tides Associated with the Eutrophication in Coastal Areas of Western Pacific

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In 1989 the international cooperative research on the outbreaks of toxic dinoflagellates in Philippines, Thailand and Brunei Darussalum were carried out.In 1989 the studies were developed to survey the distribution of Pyrodinium bahamense and toxic shellfish together with the chemical enveronmental research in Masinloc Bay and the coastal water area of Rimai of Manila Bay. The isolation and culture of Pedinomonas noctilucae were continued.Surveys in Masinloc Bay were carried out at 9 stations on July 26 - 27. The Bay is an open type with the area of 10 X 5 Km, elongated from south to north, which is located in the southern west coast of Luson Island. Salinities of the bottom water of about 20 m depth were about 30%。. It was heavy rain fall through the survey period and the salinities of surface water decreased to around 20 %。. This result shows the water qualities of the Bay are easily affected by the inflow of land water.The cell density of P. bahamense was 40 cells /ml at Oyon Bay in … More the north. The cysts in the sediment mainly distributed in central area and were counted to be 50 cells /ml but the vegetative cells were scarcely found in central and south area. Cysts which were found in Masinloc Bay were mainly heterotrophic species such as Brigantedinium spp. Diplopelta cf. parva and Spiniferites spp.PSP toxicity of P. bahamense collected from sea water was 1 MU in 11,000 cells. The toxicity of penshell and Spondylus sp. In the bottom of central area were 4 and 20 mu/g, respectively. They seemed to be intoxicated by the cysts of P. bahamense.The survey along the coast of Rimai, Manila Bay was carried out on August 2- 3.The salinities of Manila Bay were 18.49 - 22.53 %。 in surface water and 26.87 - 29.94 %。 in bottom water. Nitrate-nitrogen was in the high range of 43 - 64 muM/l and phosphate phosphorus was 3.4 - 4.1 muM/l. These values seemed to derive from proceeding of the eutrophication of the Bay.Gymnodinium catenatum which is a PSP producer was found as the first case of the Bay and cultured.HPLC analysis of PSP of cultured G. catenatum revealed the presence of C1, C2 and C4 toxins as main components. Considering from the PSP composition, G. catenatum seemed not to be responsible to the intoxication of shellfish in Manila Bay. Chattonella sp., a fish killer, was also isolated and cultured.In Gulf of Thailand, Pedinomonas noctilucae was isolated from green Noctiluca and succeeded to the culture in laboratory. The culture medium was invented according to the analytical results of N. scinitillans and pH of the medium was adjusted to 4.5 and culture temperature was maintained at 28^ﾟC. Maximum cell densities in stationary phase of the growth was about 200,000 cells/ml.Based on the results obtained in 1990, the distribution of toxic P. bahamense and its cysts in Masinloc Bay and west of the Manila Bay considerably became clear together with the shellfish toxication.The further studies on this projects will be expected to contribute to establish the countermeasures on PSP problems in south east Asia and also to promote the fundamental studies on red tide organisms. Less