The nature of the Juan de Fuca eddy: the rise and fall of domoic acid to the Washington State coast

V.L. Trainer¹, W.P. Cochlan², B.M. Hickey³, E.J. Lessard³, A. MacFadyen³, C.G. Trick⁴, and M.L. Wells<sup>5

1</sup> NOAA Fisheries, Northwest Fisheries Science Center, Seattle, WA 98112, USA
² Romberg Tiburon Center for Environmental Studies, San Francisco State University, Tiburon, CA 94920-1205, USA
³ School of Oceanography, University of Washington, Seattle, WA 98195, USA
⁴ Schulich School of Medicine, University of Western Ontario, London, Ontario N6A 5B7, Canada
⁵ School of Marine Sciences, University of Maine, Orono, ME 04469, USA

The Juan de Fuca eddy is a retentive summer feature located off Washington State, U.S.A. whose location and size is dependent on wind as well as freshwater outflow from the adjacent strait. Although domoic acid-producing Pseudo-nitzschia species have been recorded in this region since 1996, their abundance and toxicity vary from year to year in a manner that is at present unpredictable. Over the last 3 years, ECOHAB Pacific Northwest researchers have performed 5 synoptic cruises to characterize the strength and variation in the biological, physical and chemical factors pertinent to HAB success. The interdisciplinary data indicate that the eddy can be contrasted to the coastal upwelling zone by the following: (1) higher specific cellular toxicities, especially in Pseudo-nitzschia found around its edges, (2) a greater degree of iron limitation (3) a more persistent macronutrient supply. The shifting physiological health of Pseudo-nitzschia cells in transit from the eddy also points to its uniqueness. In spite of a well developed eddy in September 2004 featuring high levels of both particulate (up to 95 nM) and dissolved domoic acid (up to 20 nM), this HAB never reached the coast, illustrating that toxic events require both toxin production and onshore transport.