Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 487
Title: Recent domoic acid closures of shellfish harvest areas in Washington State inland waterways
Author: Vera L. Trainer, W. P. Cochlan, Aleta Erickson, Brian D. Bill, F. Cox, J. A. Borchert, K. A. Lefebvre
Publication Year: 2007
Journal: Harmful Algae
Volume: 6
Issue: 3
Pages: 449-459
Keywords: domoic acid, Pseudo-nitzschia, Puget Sound, shellfish closure, harmful algal bloom

Several species of the toxigenic diatom Pseudo-nitzschia, together with low concentrations of domoic acid (DA) in shellfish have been observed in Puget Sound, Washington State, since 1991.  However, for the first time in September 2003, high-density blooms of Pseudo-nitzschia forced the closure of recreational, commercial, and tribal subsistence shellfish harvesting in Puget Sound.  Here we report on the environmental conditions associated with shellfish closures in two inland waterways of Washington State during fall 2005.  In Sequim Bay, shellfish harvest losses occurred on September 12 following the measurement of elevated macronutrient levels on September 2, and a bloom of P. pseudodelicatissima (up to 13 million cells/L) on September 9.  Ambient NH4 concentrations >12 μM (measured on September 2) were likely due to anthropogenic sources, ostensibly from sewage inputs to Sequim Bay.  The closure of a Penn Cove commercial shellfish farm on October 16 was caused by a bloom of P. australis that followed a period of sustained precipitation, elevated Skagit River flow, and persistent southeasterly winds.  The relative importance of a number of environmental factors, including temperature, stratification caused by rivers, and nutrient inputs, whether natural or anthropogenic, must be carefully studied in order to better understand the recent appearance of massive blooms of toxigenic Pseudo-nitzschia in the inland waterways of Washington State.

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