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 2006(L1VASE), a modification of the L1media.PO.10-50Inorganic carbon acquistion inthree red-tide dinoflagellatesSession: PO.10 – Ecophysiology andautecologyB Rost 1 , K-U Richter 1 , N Lundholm 2 ,PJ Hansen 31 Alfred Wegener Institute for Polar andMarine Research, BREMERHAVEN,Germany2 Dept of Phycology, University ofCopenhagen, COPENHAGEN, Denmark3 Marine Biological Laboratory, Universityof Copenhagen, HELSINGØR, DenmarkCarbon acquisition wasinvestigated in marine bloomformingdinoflagellates,Prorocentrum minimum,Heterocapsa triquetra, andCeratium lineatum. Activities ofcarbonic anhydrase (CA),photosynthetic O 2 evolution, CO 2and HCO 3 - uptake rates weremeasured by membrane inlet massspectrometry in cells acclimated tolow and high pH. A secondapproach used short-term 14Cdisequilibriumincubations toestimate the carbon source utilizedby the cells. All species showednegligible extracellular CA activityin cells acclimated to low pH andonly slightly higher activities whenacclimated to high pH. Halfsaturation concentrations forphotosynthetic O 2 evolution werelow compared to RubisCO kinetics.Moreover, affinities for inorganiccarbon increased with increasingpH in the acclimation, indicating theoperation of an efficient CO 2concentrating mechanism. Rates ofHCO 3 - uptake were high in theinvestigated species, contributingmore than 80% of photosyntheticcarbon fixation. Affinity for HCO 3-and maximum uptake ratesincreased under higher pH. Modesof carbon acquisition are consistentwith the 13C-fractionation patternindicating a strong species-specificdifference in leakage. Our resultssuggest that photosynthesis inmarine dinoflagellates is not limitedby inorganic carbon even at highpH.PO.05-12Alternative bioassays for thedetection of cyanotoxinsSession: PO.05 - Toxin analysisDR RuebhartGriffith University, MEADOWBROOK,AustraliaThe principal method for detectingthe presence of unknowncyanotoxins in Australia hastraditionally been the mousebioassay. When specificcyanotoxins are suspected,instrumental methods are generallyused, but the identity of potentialcyanotoxins is not always knownand there is still the requirement fora broad screening assay for use inthe water industry. Despite thewidespread use and currentreliance on the mouse bioassay,this test has several constraints.These constraints include: lack ofprecise quantification of cyanotoxinsat low concentrations, insensitivity,difficulties in the interpretation ofresults and slow turnaround time.Additionally, animal ethicsguidelines are calling for theelimination of the use of vertebratesin applications such as toxicitytesting. This means that alternativebioassays for the detection ofcyanotoxins in water supplies need271