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Open Access Publications from the University of California

New Tools and Insight for Recognition of Pseudo-Nitzschia Bloom and Toxic Incidence


Pseudo-nitzschia is a cosmopolitan marine diatom which can cause the poisoning of humans, marine mammals, and birds through the production of the neurotoxin domoic acid and subsequent contamination of the marine food web. Severe poisoning events are induced when environmental conditions allow: (1) the rapid proliferation ('bloom') of resident toxic species of Pseudo-nitzschia, and/or (2) their enhanced toxin production, and (3) the conveyance of the toxin into prey items. The introduction of domoic acid into the food web was recognized as a public health concern along the coast of California following a Pseudo-nitzschia bloom and seabird mortality event in the Monterey Bay area in 1991, and blooms of Pseudo-nitzschia have since been observed in the region with regularity. Since the recognition of the public health concern posed by these recurrent harmful algal bloom (HAB) events, the California Department of Public Health (CDPH) has been charged with protecting the public from domoic acid intoxication through the Preharvest Shellfish Protection and Marine Biotoxin Monitoring Program. This regulatory program (1) conducts, surveys, classifies and monitors commercial shellfish growing areas, and (2) monitors numerous points along the California coastline for marine biotoxins in shellfish and toxigenic phytoplankton in the waters. While these regulatory efforts have successfully prevented significant injury to public health since they began, they remain relatively inefficient in terms of time, energy, and cost.

This thesis begins with an investigation of the environmental factors that contribute to Pseudo-nitzschia bloom formation in Monterey Bay (Chapter 1). The identification of nitrate and river discharge as seasonal bloom factors motivated an explicit evaluation and contextualization of river nitrate loading within the 'upwelling-dominated' region of Monterey Bay (Chapter 2). Finally, a new monitoring technology, Solid Phase Adsorption Toxin Tracking (SPATT), is presented, developed primarily for use by public health managers for more effective and efficient monitoring of domoic acid, the toxin produced by Pseudo-nitzschia and the ultimate cause for concern (Chapter 3, with addendum).

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