Bloom and spread mechanisms of toxic red tides in SE-Asia

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In 1993 preliminary surveys were carried out at here toxic plankton or intoxicated shellfish was reported in the Philippines and Indonesia. As extensive toxic red tides had occurred with many victims, intensive research were made at 10 areas of the Philippines. No toxic dinoflagellate was found in plankton samples , however, many cysts were in sediment in some of the areas. Paralytic and diarrhetic toxins were detected in shellfish specimens collected at Camiguin Island of Mindanao Island. This is the first finding of the diarrhetic toxins in tropical area. Causative organisms were confirmed as Dinophysis caudata and D. miles by following researches conducted at Sapian Bay, Panay Island.In 1994 the main survey was conducted in Manila Bay. Water quality was highly eutrophic. Total nitrogen was 87 muM at maximum (average 29.4 muM) and total phosphorus 10.3 muM (average 4.15 muM). As water contained more particulate matters than soluble nitrogen and phosphorus, up-take rate into phytoplankton and turn over rates of the elements were presumed to be high. Sedimentation rate was 0.91 cm/yr. at the central area and 1.5 cm/yr. at the east coast. The toxic dinoflagellate, Pyrodinium bahamense, was distributed in shallower waters than 6 m of innermost and Bataan coast areas. The resting cyst of the species was widely found in surface and deeper sediments accumulated several decades ago. Therefore the species was presumed to have been recurring in the area several times in the decades, but recently recognized after incidents of red tide and intoxication of shellfish.In Indonesia intensive surveys were conducted at Jakarta Bay and Flores Islands, but no paralytic toxin producer could be found. Benthic toxic species, Prorocentrum lima was found in Flores islands. In Malaysia Pyrodinium bahamense was found. In China Alexandrium spp. were confirmed as toxic species in southern coastal waters.