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Recent publications have identified the analysis of phycotoxins in sentinel shellfish as a problematic tool for environmental monitoring purposes. Domoic acid (DA), a neurotoxin produced by some species of the diatom Pseudo-nitzschia, can remain undetected in sentinel shellfish stocks during toxic blooms and subsequent marine bird and mammal mass mortality events. Solid Phase Adsorption Toxin Tracking (SPATT) has previously been described for monitoring of lipophilic toxins, whereas resin-based sampling methods are routinely employed for many other environmental contaminants. Here, we evaluate the applicability of SPATT for monitoring the hydrophilic phycotoxin DA and demonstrate that the same field sampling methods can be used for the detection of saxitoxins. We present laboratory-based adsorption profiles characterizing the performance of SPATT with four resin types: (1) HP20, (2) SP700, (3) SP207, and (4) SP207SS. We present results from 17 mo of approximately weekly SPATT deployments in Monterey Bay, California (USA); this period included two significant toxigenic Pseudo-nitzschia bloom events as well as low-level saxitoxin events. SPATT signaled the presence of DA 3 and 7 weeks before the recognition of bloom conditions by traditional monitoring techniques (7 and 8 weeks before shellfish toxicity). Under ambient (non-bloom) conditions, all resins detected DA when its presence was not apparent from traditional monitoring, highlighting the ubiquity of low level or transient toxin events in the environment. This study is the first to evaluate SPATT deployments in U.S. waters, and the first to demonstrate the applicability of SPATT toward detection of hydrophilic phycotoxins in the field. |
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