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 2006Phosphatases, enzymes thathydrolyze organic phosphorus,include both alkaline and acidvarieties with pH-dependent optima.Phytoplankton phosphataseresearch has focused primarily onalkaline phosphatase expression inphotosynthetic species, includingdinoflagellates. Acid phosphataseshave been less studied in algae andhave been examined in very fewdinoflagellates (Lingulodiniumpolyedrum, Schmitter andJurkiewicz 1981; Crypthecodiniumcohnii, Barlow and Triemer 1986).Traditionally, phosphatase activityhas been measured usingcolourimetric or fluorometricmethods that cannot resolvevariability within populations andamong taxa in mixed assemblages.Recently, the molecular probe ELF-97® (Enzyme-LabelledFluorescence; Molecular Probes,Inc., Eugene, OR) was developedfor in situ fluorescencemeasurements of both alkaline andacid phosphatases in individualcells. In this study, ELF-97® wasused to examine phosphataseactivity in the heterotrophicdinoflagellate Pfiesteriashumwayae. Phosphatase activityalso was evaluated at different pHvalues using colorimetric methods.Active phosphatases generally werelocalized in dense deposits near orsurrounding the food vacuole. Thelocation of enzyme activity andsupporting colorimetricmeasurements suggest that acidphosphatases predominate in P.shumwayae and have a generalcatabolic function.PO.13-22Field and laboratory mortalityand bloom decay rates ofGymnodinium catenatum:improving parameters in coastalmodelsSession: PO.13 - Regional eventsJH Skerratt, A Holmes, S BlackburnCSIRO, HOBART, AustraliaPhytoplankton mortality is rarelyaddressed in ecological models yetis seen by both modellers andecologists as significant. Mortalityrates of a number of micro-algalspecies present in the Huon EstuaryTasmania, Australia were assessedusing both laboratory and field data.Particular emphasis was placed onGymnodinium catenatum, a harmfuldinoflagellate that forms recurrentblooms in the estuary. Mortalityrates are new in marine ecologicalmodels so we transferredmethodology and techniques frombacterial mortality models as thesehave been extensively researchedbecause of food pathogens.Mortality rates for all microalgalspecies tested in the laboratorywere between 0.04-0.3/day andfield data for G. catenatum bloomsfrom 1989 to 2004 concurred withthese rates of decline. The mortalityrates will be incorporated into thepresent biogeochemical models ofthe estuary and surrounding waters.PO.10-12Growth preferences and toxicityof Chattonella aff. verruculosa(Heterokontophyta)Session: PO.10 - Ecophysiology &autecologyB SkjelbredUniversity of Oslo, OSLO, NorwayThe heterokont flagellate under theprovisional name Chattonella aff.verruculosa has formed recurrent281