First surveys of toxin content in bivalves and potentially toxic phytoplankton in exposed marine areas of the southeastern Bay of Biscay

In order to protect public health, phytoplankton and phycotoxin monitoring programs have been implemented in shellfish aquaculture areas worldwide. In the Basque Country (northern Spain) there is a recent interest in the... [ view full abstract ]

In order to protect public health, phytoplankton and phycotoxin monitoring programs have been implemented in shellfish aquaculture areas worldwide. In the Basque Country (northern Spain) there is a recent interest in the production of bivalves offshore. However, until now, studies focused on toxicity risk had not been conducted in these waters. Here, the abundance of potentially toxic species and toxin content in mussels (Mytilus galloprovincialis) are described within a pilot scale farm located at a depth of 50 m. Before starting commercialization, sampling campaigns have been conducted from May 2014 to present. Mussels were obtained from the upper meters of the culture, whereas water samples for phytoplankton identification were taken at 3‒6 discrete depths from surface to near bottom. Available data up to December 2016 (28 surveys) indicate the presence of toxins associated to risk of paralytic shellfish poisoning in 3 occasions, but always below the maximum limit allowed for commercialization. Lipophilic toxins surpassed their legal limit in 1 out of 9 samples analyzed by the mouse bioassay (up to December 2014). From January 2015 thereon, analytical techniques indicated the presence of okadaic acid (a diarrheic toxin) and yessotoxins (cardiotoxicity risk), but only the diarrheic toxin surpassed its legal limit (in 1 out of 19 samples). The concentrations of okadaic acid and yessotoxins seemed to be in accordance with the cell abundance of two potentially causative species (Dinophysis acuminata and Lingulodinium polyedra, respectively). Finally, although Pseudo-nitzschia spp. was frequently found, domoic acid (the amnesic toxin) was not detected.