Domoic Acid and Pseudo-nitzschia off the Washington Coast: The first season of ECOHAB Pacific Northwest cruises

Vera L. Trainer¹, Barbara M. Hickey², Nicolaus G. Adams¹, Bich-Thuy L. Eberhart¹, Julian Herndon³, and William P. Cochlan³

1 NOAA Fisheries, Northwest Fisheries Science Center, Seattle, WA 98112, USA
2 School of Oceanography, University of Washington, Seattle, WA 98195, USA
3 Romberg Tiburon Center for Environmental Studies, San Francisco State University, Tiburon, CA 94920-1205, USA

Pseudo-nitzschia spp. are frequently observed over the continental shelf off Washington, near the Washington coast and in the Juan de Fuca eddy between Washington and British Columbia. Measurements made during cruises and beach sampling of seawater and shellfish in 1997 and 1998 were consistent with the possibility that domoic acid (DA) from the Juan de Fuca eddy appears to move southward in prolonged upwelling events and then onshore during the first major storm of the fall season, resulting in elevated concentrations of DA in razor clams on coastal beaches. Such events result in immediate closure of coastal clamming beaches, often for the entire season (or longer, due to the slow depuration of DA from razor clam tissue). During our first two ECOHAB cruises, an objective was to determine: (1) the distribution of Pseudo-nitzschia spp. in the eddy and coastal upwelling regimes, (2) the production of DA and release by Pseudo-nitzschia in response to environmental conditions, and (3) the potential impact of macronutrient availability on toxin production. We measured both particulate and dissolved levels of DA by receptor binding assay and enzyme linked immunosorbent assay near the Juan de Fuca eddy and off the Washington coast to determine the spatial distribution of toxin during the early (June) and late (September) upwelling seasons. Low but measurable levels of particulate DA were measured in the eddy, off the central coast near Kalaloch beach, Washington State, and off Barkley Sound, British Columbia, Canada. In early June particulate DA measured less than 30 pM in the eddy region, but increased to a maximum of 500 pM in surface waters after a storm in mid-June. Depth profiles of particulate DA to 50 m indicated that the highest levels were concentrated in the upper 10 m of the water column and at frontal zones near the edge of the eddy. Shipboard analysis of DA allowed a responsive sampling strategy to be used for onboard nutrient manipulation and grazing studies.