Field observations of the dinoflagellate genus <i>Azadinium</i> and azaspiracid toxins in the south-west Atlantic Ocean

Abstract

Some dinoflagellate species of the genera <i>Azadinium</i> and <i>Amphidoma</i> (Amphidomataceae) produce azaspiracids (AZA), a group of toxins responsible for gastrointestinal disorders in humans following the consumption of contaminated shellfish. In this study, we investigated the diversity, distribution and abundance of <i>Azadinium</i> and AZA from field plankton samples collected during four oceanographic expeditions that covered an extended area of the Argentine Sea during different seasons. Scanning electron microscopy analyses indicated the presence of five <i>Azadinium</i> species: <i>Az. dexteroporum</i>, <i>Az. luciferelloides</i>, <i>Az. obesum</i>, <i>Az. asperum</i> and <i>Az.</i> cf. <i>poporum</i>. <i>Azadinium</i>-like cells were frequently found and were even an abundant component of plankton assemblages, showing a wide latitudinal distribution, from ~38 to ~55.5°S, and occurring in a wide temperature and salinity range. High cell densities (up to 154000cellsL⁻¹) occurred in northern slope and external shelf waters during spring. AZA-2 was detected in net samples from the 20- to 200-µm fractions by tandem mass spectrometry–liquid chromatography analysis, suggesting a transfer of AZA through the food web. Our results contribute to the knowledge of the worldwide occurrence of <i>Azadinium</i> species and AZA, and highlight the importance of amphidomatacean species as a potential source of AZA shellfish poisoning in the south-west Atlantic Ocean.