The risk of amnesic shellfish poisoning from Pseudo-nitzschia sp. blooms and subsequent domoic acid events has persisted in Monterey Bay on the central California coast for nearly three decades. Over this time, HAB monitoring has experienced rapid advancement in methods and technologies designed to predict toxic blooms and mitigate losses. One such innovation, solid phase adsorption toxin tracking (SPATT), is now widely applied for passive sampling of dissolved toxins, often complementing toxin

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... quantification from shellfish and direct measurements from seawater. Here we show 10 years (2010 - 2020) of domoic acid measured by SPATT in Monterey Bay and investigate trends in relation to key environmental factors. Of the three SPATT resins deployed (HP-20, SP-207, and SP-700) results indicate subtle differences that may affect how well domoic acid from SPATT resembles toxin accumulation in shellfish. In recent years, SPATT samples contained higher levels of domoic acid than might be expected by direct analysis of seawater and extractions from mussels. Analysis of monitoring data from the Santa Cruz Wharf repository revealed complex relationships between passive sampling, cell counts, and direct analysis from seawater, though there was a negative correlation between all toxin parameters and nutrient concentrations. To our knowledge, this is the longest dataset for detecting domoic acid by SPATT. Continued analysis may give insight on future trends and greater understanding of the environmental drivers of dissolved marine biotoxins in Monterey Bay.