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 2006Atlantic European coasts. It is theprincipal cause of diarrhetic shellfishpoisoning (DSP) toxic episodes in aseafood production area in the EbroDelta, Spain.This species has beenfound to produce okadaic acid(Delgado et al. 1996). As for otherspecies of the genus Dinophysis, itis not yet possible to obtain culturesthat would facilitate its study.A bloom of D. sacculus wasdetected in a small pond connectedto Alfacs Bay during the fall of 2005and winter of 2006. This hasallowed us to make an estimation ofthe toxin profile of this species inthis area. In some samplescollected within this period, D.sacculus represented more than the90% of the phytoplanktonpopulation with concentrations up to81600 cells/L. Cytotoxic assays andanalytical procedures were used toidentify the toxins and the toxinpotency of this species. The toxicityof this species was evaluated withcell viability (MTT assay), IC 50 wasdetermined as well as themorphological changes. LC-MSanalysis allowed the detection ofPTX2, PTX2sa and okadaic acid.PO.14-10Removal of red tide organisms byorgano-clays: removalmechanisms and ecologicaleffectsSession: PO.14 - MitigationXihua Cao, Yonghui Gao, Zhiming YuIOCAS, QINGDAO, ChinaSeveral organo-clays wereprepared by modification of clayswith different quaternary ammoniumcompounds (QACs). Themodifications influenced thecapacity of the organo-clays toremove red tide organisms. Theremoval mechanisms andecological effects are discussed.Hexadecyltrimethylammonium(HDTMA) bromide improved thecapacities of clays to flocculate thealgae. One of the reasons was thatHDTMA in metastable state wastoxic to the algae. The influence ofthe organo-clays on nutrients, DOand COD in seawater was alsostudied. The organo-clays hadbetter capacity to adsorb nutrients,especially phosphate, than theoriginal clays. Seawaterparameters, such as DO, COD andpH also improved after treatment ofharmful algal blooms by the organoclays.The clays not only controlledHABs effectively, but also benefitedseawater quality. Experiments in aco-culture system indicated that thered tide organisms (Heterosigmaakashiwo, Prorocentrumdonghaiense) could be efficientlyextinguished without any evidentimpact on co-cultured organismssuch as Crassostrea gigas.PO.16-14Sexual compatibility assays inPseudo-nitzschia species fromthe Aveiro coastal lagoon (NWPortugal)Session: PO.16 – Life cyclesCC Carreira 1 , CI Churro 1 , AJ Calado 1 ,Ø Moestrup 2 , N Lundholm 21 University of Aveiro, AVEIRO, Portugal2 Dept Phycology, Copenhagen University,COPENHAGEN, DenmarkPortuguese isolates of the followingfive Pseudo-nitzschia species weremixed and tested for the capacity tomate and produce auxospores:Pseudo-nitzschia americana, P.australis, P. fraudulenta, P.multistriata and P. pungens.Additionally, sexual compatibilitywas assayed with strains from St.Lawrence, Canada (P. fraudulenta),146