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 2006software. The resources of allnodes will be linked so that contentfrom all local sites, as well asexternal resources accessedthrough linkouts, can be accessedfrom each node. PLANKTON*NETwill use taxonomically intelligentweb services developed by the uBioProject (http://www.ubio.org) toorganize information aboutorganisms. The modular softwarewill also be extended to containenvironmental data.PLANKTON*NET already containsmany records of harmful algae incollections from very differentgeographic areas and the coveragewill increase as new partners maketheir data collections visible throughPLANKTON*NET. By providingcomprehensive, reliable up to dateinformation it will present a valuableresource for research andmonitoring studies on harmfulalgae.PO.07-09Effects of nutrient supply ratiosand initial communitycomposition on dinoflagellatebloom formation: mesocosmstudies from the northern BalticSeaSession: PO.07 - Ecology andoceanographyA Kremp 1 , T Tamminen 2 , K Spilling 21 University of Helsinki, HANKO, Finland2 Finnish Environment Institute, HELSINKI,FinlandSince the early 1980s 'red-tides'caused by cold-waterdinoflagellates have become aregular phenomenon in the coastalN Baltic Sea, where theyincreasingly replace the typicaldiatom-dominated phytoplanktonspring bloom assemblage. Althoughthis trend has generally beenrelated to anthropogenic nutrientenrichment and changing climaticconditions, the mechanismsunderlying the relationship haveremained poorly understood. Usingmesocosms, we studied the effectsof variable nutrient additions andnutrient supply ratios on speciescomposition and dominancepatterns of natural springphytoplankton communities from thecoastal N Baltic Sea. Theexperiments which were repeatedduring 3 consecutive years showedthat bloom formation anddominance of the dinoflagellateWoloszynskia halophila primarilydepended on the size of theinoculum population and the relativeabundance of co-occurring diatoms.Variations of N/P:Si ratios did nothave any significant effect onphytoplankton development andcomposition. Addition of N and P aswell as increased irradiancegenerally stimulated the growth ofdiatoms, but could not alter theoutcome of competition betweendiatoms and dinoflagellates whenthe latter were initially dominant.Our results emphasize theimportance of efficient recruitmentstrategies and initial conditions indinoflagellate bloom formation.PO.05-10Yessotoxin profiles from culturesand planktonic field samples ofthe marine dinoflagellatesProtoceratium reticulatum andGonyaulax spiniferaSession: PO.05 - Toxin analysisB KrockAlfred-Wegener Institute for Polar and M,BREMERHAVEN, GermanyYessotoxins are a large group ofladder-frame disulfated polyethers.Yessotoxin and an array of209