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 2006technologies and/or alternativemanagement strategies will benecessary to enable DoD vessels tocomply with proposed standards.PO.04-06Lethality of microalgae to farmedAtlantic salmonSession: PO.04 – Food chainsLE Burridge, JL Martin, M Lyons, MMLeGresley, BD ChangFisheries and Oceans Canada, ST.ANDREWS, NB, CanadaBlooms of phytoplankton in the Bayof Fundy have been implicated inthe deaths of farmed Atlanticsalmon. To establish whether or notelevated concentrations of thesealgae can cause mortality,monocultures of two species ofmicroalgae, Alexandrium fundyenseand Ditylum brightwellii were grownin large quantities. Atlantic salmonsmolts were exposed to a range ofconcentrations of these cultures for24 h and an LC50 was determinedaccording to the concentration ofcells present (cells/L). Fishexposed to Ditylum brightwellii atconcentrations as high as 10 6cells/L had no apparent deleteriouseffect. This concentration is wellabove the concentration observedin the field. Salmon exposed to A.fundyense were affected. The LC50was estimated to be ~300,000cells/L - a concentration that hasbeen observed in the field.Alexandrium fundyense is a knownneurotoxin producer and is theorganism responsible for causingparalytic shellfish poisoning. Work iscontinuing to determine if otherspecies found in the Bay of Fundycan cause problems for cultured fishand to determine the concentrationsof toxins in the Alexandrium culturesand fish tissues.PO.08-27Variations in growth and toxicityof Gymnodinium catenatum fromthe Gulf of California underseveral ratios of nitrogen andphosphorusSession: PO.08 - ToxicologyJose Bustillos-Guzman 1 , IsmaelGarate-Lizarraga 2 , FranciscoHernandez-Sandoval 1 , L. Morquecho 1 ,C. Band-Schmidt 21 CIBNOR, LA PAZ, Mexico2 CICIMAR, LA PAZ, MexicoOne anthropogenic influence on thecoastal waters is the input ofnutrients, which is reflected in theincrease and selectivity of particularautotrophic organisms.Gymnodinium catenatum Graham isa PSP producer, widely distributedalong the Pacific coast of Mexico,linked to poisoning events in coastalwaters, as well as poisoning ofshellfish consumed locally. In thisstudy, G. catenatum was submittedto several nutrient scenarios tomeasure its growth and toxinproduction. The greatest densityoccurred at the 16:1 ratio, producing33% more cells than the 32:1 and64:1 ratios, which, in turn had 34and 30% more cells than the 1.6:1and 3.2:1 ratios. Total toxicity wasnot affected by the treatments butdepended on the growth phase. Ingeneral, toxicity decreased slightlyover time, but increased at the endof the decay phase. The toxin profilewas dominated by sulfocarbamoyltoxins (C types) with about 60 to70% on a molar basis, followed bythe carbamoyl toxins with about 5 to25% on a molar basis. These datasuggest that changes N:P ratios willnot stimulate toxicity production, butwill mainly effect the growth of G.catenatum.143