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 2006However, D. acuminata cannot begrown in cultures, while P. lima can,and therefore P. lima cultures areused widely in OA-related studies.In this study, a toxic P. lima strainwas grown in batch cultures under:1) N-NO 3 - sufficient, 2) N-NO 3-deficient, 3) P-PO 4 3- deficient and 4)N-NH 4 + sufficient conditions for 57days. Cell numbers, growth rates,chlorophyll a, OA concentrationsper cell and nutrient concentrationsin the culture media weredetermined at regular intervals.Phosphorus was exhausted in theP-deficient and N-NO 3 - sufficienttreatments after the end of thetypical exponential phase. Nitrogendecreased but was not exhausted inany treatment. In all treatments,maximum OA concentrations percell were observed after the end ofthe typical exponential phase, whengrowth rates decreased. However,the highest OA concentration in P.lima cells was found in the P-deficient treatment (2 times higherthan any other treatment), probablydue to further limitation of growthinduced by the heavy deficiency ofphosphorus.PO.11-05Talk to me – communicationbetween cyanobacteria via toxinsand promotion of oxidative stressSession: PO.11 - AllelopathyMaria Vasselikaki, StephanPflugmacherIGB, BERLIN, GermanyCyanobacteria are now common inmany freshwater lakes and riversthroughout the world and are knownto produce a variety of different,often toxic, secondary metabolites.The ecological use of thesemetabolites is still under discussion.One main idea on cyanotoxinsmight be the use as info chemicalsbetween algal cells in the interactionof algae and macrophytes. Thisstudy investigates the idea thatcyanobacterial toxins are acommunication tool betweendifferent cyanobacteria. Thiscommunication might be an indirectone, as cyanotoxins might be atrigger for the promotion of oxidativestress, generating reactive oxygenspecies, which are known to act ascell signals. The existence ofseveral antioxidative enzymes likessuperoxide dismutase, peroxidasesand catalases as markers foroxidative stress in Synechocystissp. will be shown as well as celldamage by extensive generation ofROS like lipidperoxidation due toexposure of Synechocystis sp. tothe cyanobacterial toxin microcystin-LR. As reactive oxygen species arealso thought to have an importantrole in the communication in cells,the main hypothesis presentedhere, is that the communicationbetween cyanobacterial speciesmight be mediated by ROS and theantioxidative cycle.PO.13-76Space distribution of potentiallyharmful species on the coast ofthe state of São Paulo, Brazil(July/04-May/06)Session: PO.13 - Regional eventsMC Villac, VAP Cabral, TO PintoUniversidade de Taubaté, TAUBATÉ, SP,BrazilThis study reports on the spacedistribution of potentially harmfulspecies on the coast of the State ofSão Paulo, Brazil (July/04-May/06),based on a survey carried out incooperation with the StateEnvironmental Agency andmariculture farms to provide299