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 2006PO.13-11Crassostrea ariakensis and C.virginica responses toichthyotoxic KarlodiniumveneficumSession: PO.13 - Regional eventsSG Sellner 1 , EF Brownlee 2 , KGSellner 3 , A Place 4 , JE Adolf 4 , HNonogaki 4 , TR Bachvaroff 41 Morgan State University ERC, ST.LEONARD, MD, United States of America2 Hood College, FREDERICK, MD, UnitedStates of America3 Chesapeake Research Consortium,EDGEWATER, MD, United States ofAmerica4 UMD Center of Marine Biotechnology,BALTIMORE, MD, United States ofAmericaThe Eastern oyster Crassostreavirginica and the Asian oyster C.ariakensis are native and potentiallyintroduced oysters, respectively, inthe Chesapeake Bay and as such,will be exposed to the naturalphytoplankton assemblagesincluding harmful speciesthroughout their life cycles. Recentwork suggests that at least one ofthese prey items, the ichthyotoxicdinoflagellate Karlodiniumveneficum, occurs frequentlythroughout the growth period for theoysters and produces linearpolyketide toxins (karlotoxins) whichelicit toxicity through steroldependent,non-specific membranepores. Spat and juvenile oysters ofeach species were exposed tomoderately toxic strains [18.5 ± 6.2ng ml -1 ] at environmentally-relevantcell densities and growth andclearance rates contrasted withrates observed on otherphytoplankton species, including thespring bloom former Prorocentrumminimum and phytoplanktonmixtures routinely used in oysterhatcheries. Spat growth andclearance rates and juvenileclearance rates of both oysterswere significantly reduced whenfeeding on Karlodinium, relative tothe other prey species. These initialresults suggest that thecosmopolitan Karlodiniumveneficum inhibits growth and wouldpotentially curtail oyster productionwithin the tidal bay and its tributariesthroughout the oysters' growthperiods and considering its globaldistribution, potential impactthroughout temperate areas shouldbe assessed.PO.13-89The present state of toxinproducing cyanobacteia speciesin the southern Lake Victoria(Tanzania)Session: PO.13 – Regional events1 Pazi M. Semili, 2 Dickson K.Rutagemwa, 3 Hassan J. Mjengera1 Faculty of Aquatic Sciences andTechnology (FAST), University of dar esSalaam, DAR ES SALAAM,Tanzania2 Lake Victoria Environmental ManagementProject, MWANZA, Tanzania3 Ministry of Water, Water LaboratoriesUnit, DAR ES SALAAM, TanzaniaCyanobacterial blooms havebecome an increasing worldwideproblem in aquatic habitats. Theseoccurrences can be partiallyattributed to gradual eutrophicationof waterways caused by increaseof nutrient inputs. Certain speciesof cyanobacteria produce toxinsand, as a result, blooms createmajor threats to animal and humanhealth, tourism, recreation, andaquaculture. Despite these facts,studies on toxic cyanobacteriaspecies and their associatedenvironmental factors are limited inthe tropics. Worse still, in EasternAfrica, farmers and the generalpublic are not aware of thechallenges posed by toxin-277