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 2006Growth control of toxicmicroalgae by weak voltage andweak currentSession: PO.14 - MitigationYukie Hatta, Asami Touna, HitoshiOgawaUniv. Tamagawa, MACHIDA-SHI TOKYO,JapanIt is well known that the weakvoltage and current in the nervoussystem influence the physiology ofanimals. On the other hand, little isknown about the influences ofvoltage and the current on thephysiology of algae and plants.The use of a slight voltage andcurrent was reported as adhesionprevention of the barnacle by Inoueet al. (Fisheries Engineering inJapan 2004 Vol. 41 No1. pp. 47-52).With a relatively low voltage (3 to12V) movement to the electrode(30 cm between the electrodes)and whitening of the toxicmicroalgae was observed.Intermittent and intersectionvoltage and current supply havepossible effects on the growth ofthe algal cell.The voltage and the current supplyhave influence on surfacing andsedimentation of the algae. Effectsof daytime and nighttime was alsoseen.The electrical stimulations maycause disturbance and confusion ofelectrical potentials of the cell filmsand thereby influence mineralnutrition, oxygen and carbondioxide intake of the cells.PO.04-11Uptake, metabolism and loss ofclay-flocculated brevetoxins in asurface deposit-feeding clamSession: PO.04 – Food chainsAG Haubois, M Bricelj, M QuilliamNational Research Council of Canada,HALIFAX, CanadaBlooms of the brevetoxin-producingKarenia brevis in the Gulf of Mexicocause fish kills, food poisoning andrespiratory irritation in humans.Sedimentation of toxic cellsfollowing clay application couldreduce toxin incorporation bycommercially important suspensionfeedingbivalves and direct publichealth impacts, but may potentiallylead to brevetoxin (PbTx)accumulation by benthic depositfeeders.The goal of this study wasto determine whether depositfeedingcould provide a pathway oftoxin transfer from deposited clay-K.brevis aggregates. We investigatedPbTx uptake, metabolism anddetoxification kinetics in a depositfeeding,tellinid clam exposed toclay-deposited brevetoxins. Wedemonstrate that brevetoxins canbe rapidly accumulated by depositfeedingfrom sedimented K. breviscells (exceeding the regulatory levelof 0.8 mg PbTx g -1 within ~12h asdetermined by ELISA). LC-MSanalysis showed that PbTx-2, thedominant toxin in the clay/cell layer,was rapidly transformed into PbTx-3and its cysteine derivatives in clamtissues. Detoxification of tissuesfollowing deposit-feeding occurredbut toxicities remained around theregulatory level for 15 days. Thistoxicity was due largely to thepersistence of the more potentPbTx-3-cys metabolites in tissues.Deposit-feeding clams do not posea direct threat to humans but mayprovide a pathway for brevetoxinfood web transfer.PO.05-09188