12th International Conference on Harmful Algae

INTERNATIONAL SOCIETY FOR THE STUDY OF HARMFUL ALGAE12 th <strong>International</strong> <strong>Conference</strong> on Harmful Algae, Copenhagen, Denmark, 4-8 September 2006occurred in the bay, weinvestigated the field conditions ofthe red tide and conducted nutrientaddition experiments on watersamples from the red tide and nonred-tidewaters to examine whetherthe red tide would be sustainedwith and without added nutrients orwould collapse rapidly in bottles.Chl a was high in the red tidepatch, but nutrients (NO 3 , PO 4 ,SiO 4 , and NH 4 ) were all low in thenon-red-tide waters, suggestingthat nutrients are not a directdriving cause for the formation ofthis high biomass red tide. Duringthe incubation, phytoplanktonbiomass gradually decreased over9 days in the red tide watersamples without nutrient additionsand without N additions andsteadily increased with N additionsuntil day 7. In the non-red-tidesamples, additions of all NO 3 , PO 4 ,and SiO 4 did not produce high S.trochoidea biomass, indicating thatfactors other than nutrientspromoted the red tide formation ofthis species.PO.14-14Control of cell growth ofcyanobacterial cells using extractfrom water grasses and leaves ofevergreen treesSession: PO.14 - MitigationHiroshi Yoshida, Yukie Hatta, ShinTakano, Ayaka Ishiguro, Asami Touno,Hitoshi OgawaUniv. Tamagawa, MACHIDA-SHI TOKYO,JapanGrowth inhibitors againstcyanobacteria were identified inextractions from various plants,andapplied to small surfaces of watersuch as drinking water reservoirsand recreational lakes. It is wellknown that cyanobacterial bloomsdo not form in some eutrophicponds. In these cases, leaves oftrees around the ponds fall into theponds, or some macrophytes growin the ponds. As a possibility, wethought that water-extractablecompounds from the macrophytesand /or the leaves affect the cellgrowth of cyanobacteria.In order to examine the cell growthinhibitory activity of waterextractable compounds from themacrophytes and the leaves,various plants were collected andextracted with water. We foundseveral inhibitory activecompounds from wood, flowerpetals and young leaves. Thecompounds were isolated andpurified from the extracts foridentification of chemical structurePO.16-04Overwintering of Heterocapsacircularisquama (Dinophyceae)as a pellicle cyst induced by lowtemperature in the laboratorySession: PO.16 – Life cyclesTakahiI Yoshida, Yuya Takahashi,Kanae Ishikawa, Ming-Key Wang,Shingo HiroishiFukui Prefectural University, OBAMA,JapanRed tide blooms of Heterocapsacircularisquama Horiguchi causemass mortality of bivalves andpresent a serious problem forshellfish aquaculture in westernJapan. Sexual reproduction has notbeen found in H. circularisquama,and the mechanism of overwinteringof the populations blooming inJapanese waters is unclear.Dinoflagellate temporary cysts arenon-motile and formed fromvegetative cells by shedding of thetheca (pellicle cyst). We proposethat the pellicle cyst of H.308