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 2006TBT growth on NH 4+(1.0 div day -1 ),followed by urea (0.8 div day -1 ),glutamate (0.54 div day -1 ), and NO 2-(0.48 div day -1 ). Growth rate vs.irradiance curves revealed that thetested forms of organic nitrogen donot enhance growth of the TBT atany irradiance above that observedfor NH 4 + grown TBT. Wehypothesize that the TBT mayutilize ambient DON to sustaingrowth at lower rates when DINbecomes limiting.PO.10-21Nitrate and phosphate uptakekinetics of the dinoflagellateAlexandrium tamarense inrelation to N:P supply ratiosSession: PO.10 - Ecophysiology &autecologyAI Murata, SCY Leong, S TaguchiSoka University, HACHIOJI, JapanNitrogen (N) such as nitrate, andphosphate (P) are primary nutrientsin coastal ecosystems. Theirconcentrations vary so dramaticallythat phytoplankton is bound to beexposed to variable N:P supplyratios. The present studyinvestigated nitrate and phosphateuptake parameters of A. tamarensein relation to N:P supply ratios in asemi-continuous experiment.Alexandrium tamarense was grownat five different N:P supply ratios(N:P = 4, 8, 16, 32 and 64) bykeeping phosphate concentration at1.56 μM-P with variable nitrateconcentrations. Increasing the N:Psupply ratios induced a decrease incellular nitrate uptake rates.However, cellular phosphate uptakerate showed a maximum value atthe N:P supply ratio 16. The cellularC:N ratio decreased with increasingN:P supply ratio, and reachedminimum value at high N:P supplyratios. This suggests that thedinoflagellate may responddifferently to nitrate or phosphatedue to N:P supply ratio. Therefore,the N:P supply ratio in coastalenvironments should be taken intoconsideration when assessing thenutrients utilized by dinoflagellatessuch as Alexandrium species.PO.13-72Brevetoxin contamination iscommon in fish from the easternGulf of MexicoSession: PO.13 - Regional eventsJ Naar 1 , LJ Flewelling 2 , JH Landsberg 21 Center for Marine Science-UNCW,WILMINGTON, NC, United States ofAmerica2 Fish and Wildlife Research Institute, STPETERSBURG, FL, United States ofAmericaBrevetoxins are potent neurotoxinsproduced by a few species ofharmful algae, most notably Kareniabrevis. These toxins are highlyichthyotoxic, leading to massive fishkills during red tide events. Fishcan be exposed to brevetoxins byabsorption of dissolved toxinthrough the gills, or by ingestion ofK. brevis cells or toxic prey such asshellfish, seagrass or zooplankton.Although very susceptible to solublebrevetoxins, a series ofexperimental exposures of fish tocontaminated prey revealed thatichthyotoxicity is modulated by theroute of exposure which allows forfish survival and toxin accumulationin tissues by dietary transfer.In light of these results and giventhe involvement of brevetoxincontaminatedfish in a 2004bottlenose dolphin mortality 1 , livefish throughout the Gulf Coast ofFlorida (n>500, more than 69distinct species) were collected andanalyzed. Our results indicate that247