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 2006Sampling was performed in 240beaches along the Catalan coast(CSIC_Agència Catalana del’Aigua) and 80 beaches along theBalearic Islands (CSIC_Conselleriadel Govern Balear). Resultsrevealed the widespread distributionof the genus Ostreopsis in thebathing waters of these tworecreational coastal areas.Concentration of the organismaround 200 cells l -1 is a commonsituation in the water column and inseveral occasions concentrations ashigh as 10 4 cells l -1 have beendetected.PO.01-22Testing the hypothesis oftemperate Asia origin ofAlexandrium catenella in ThauLagoon (NW Mediterranean)using microsatellite markersSession: PO.01 - GeneticsE Masseret 1 , S Nagai 2 , D Grzebyk 1 , BGenovesi-Giunti 1 , B Lasserre 1 , MLaabir 1 , D Alrivie 1 , Y Collos 1 , AVaquer 1 , P Berrebi 11 University Montpellier II, MONTPELLIER,France2 National Research Institute of Fisheries,HIROSHIMA, JapanA massive bloom of Alexandriumcatenella associated with paralyticshellfish poisoning first occurred inThau Lagoon (FrenchMediterranean) in 1998. Since then,A. catenella has been repeatedlyblooming in this lagoon. Morerecently, A. catenella blooms alsooccurred for the first time in severalareas in the NW Mediterranean(Spain, Italy) where this speciesseems to be expanding. On thebasis of genetic analyses of A.catenella strains isolated from theNW Mediterranean, using rDNAmarkers, it was suggested that thisMediterranean population couldhave been introduced fromtemperate Asia (e.g. Japan) throughballast waters. In order to test thishypothesis, we carried out a geneticanalysis of French Mediterraneanand Japanese strains usingmicrosatellite markers (MS). MSsequences are highly polymorphicmarkers, which are nowadayswidely used to study populationgenetics in terrestrial and aquaticmacroorganisms. This approachhas been recently used toinvestigate genetic diversity inphytoplankton. MS have beendeveloped in A. catenella (Nagai etal., Molecular Ecology Notes 6:120-122, 2006). Using these markers,we will present the comparativeanalysis of A.catenella strainsisolated from Thau Lagoon (fromblooms and resting cysts) and fromJapanese waters. The data arediscussed with respect to analysesbased on rDNA data.PO.11-06Inhibitory effects of diatoms onthe growth of the dinoflagellateAkashiwo sanguineaSession: PO.11 - AllelopathyT Matsubara, S Nagasoe, Y Yamasaki,T Shikata, Y Shimasaki, Y Oshima, THonjoGraduate School, Kyushu University,FUKUOKA, JapanResults of phytoplankton highfrequencystudies over four years inHakozaki Harbour, Hakata Bay,Japan, showed that thebacillariophytes Skeletonemacostatum and species of the genusChaetoceros are dominant in springand summer, whereas Asterionellajaponica is dominant in the fall. Onthe other hand, the density ofAkashiwo sanguinea began toincrease during early fall, when the236