DOMOIC ACID IN PSEUDO-NITZSCHIA CUSPIDATA FROM WASHINGTON STATE COASTAL WATERS

Brian D. Bill¹, Nina Lundholm², Laurie Connell³, Keri A. Baugh¹, Vera L. Trainer¹

¹NOAA Fisheries, Marine Biotoxins Program, Seattle, WA 98105, USA
²University of Copenhagen, Marine Biological Laboratory, DK-3000 Helsingør, Denmark
³University of Maine, School of Marine Sciences, Orono, ME 04469, USA

During the September 2004 ECOHAB-Pacific Northwest cruise, a toxigenic bloom of Pseudo-nitzschia cuspidata (Hasle) was found to encompass a 30-mile wide area south of Vancouver Island and west of Washington State. Over 94% of the total Pseudo-nitzschia observed in samples from this Juan de Fuca eddy region were P. cuspidata. Particulate domoic acid (DA) levels reached 1.3 pg DA cell^-1 with maximum cell densities of 13 x10⁶ cells L^-1. Cultures were established and grown on nutrient enriched seawater media to verify toxin production by P. cuspidata. Particulate DA levels in cultures reached 0.02 pg DA cell^-1 and maximum cell numbers were 3 x10⁸ cells L^-1. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were both necessary to obtain information on species specific characteristics due to the morphological similarities of the species within the P. pseudodelicatissima / cuspidata complex. Based on small subunit (SSU) ribosomal gene comparisons, P. cuspidata is most closely related to P. delicatissima and most distant from the P. multiseries / P. pungens / P. australis clade. No confirmed P. pseudodelicatissima isolates were available to include in this study. Additionally, whole cell hybridization assays were performed onboard using species specific large subunit (LSU) ribosomal directed probes. The P. pseudodelicatissima probe muD2 did not cross react with P. cuspidata. The development of a species-specific probe for P. cuspidata could lead to a more timely identification and assessment of the potential toxic threat of this species to marine resources.