Bloom of Dinophysis spp. dominated by D. sacculus and its related diarrhetic shellfish poisoning (DSP) outbreak in Alfacs Bay (Catalonia, NW Mediterranean Sea): Identification of DSP toxins in phytoplankton, shellfish and passive samplers

We report a comprehensive study of a diarrhetic shellfish poisoning (DSP) outbreak in a Mediterranean coastal embayment, integrating phytoplankton identification and quantification data, with toxin analysis by LC-MS/MS of shellfish samples (mussels and oysters), phytoplankton concentrates, and solid phase adsorbing toxin tracking (SPATT) devices. Alfacs Bay was proposed as a model for the study of semi-enclosed coastal embayments and it is the most important shellfish farming area in Catalonia (Spain, NW Mediterranean Sea). The bay suffered a ban for bivalve harvesting that lasted 78 days, from late winter to the end of the spring of 2012, due to a harmful algae bloom of the toxic dinoflagellate Dinophysis sacculusthat fluctuated in three abundance peaks, reaching maximum abundance of 2200 cell/L. Mussels sampled during the bloom contained okadaic acid (OA, maximum 592 μg/kg, 3.7 times the maximum permitted level (MPL) set by the European Commission), and pectenotoxin-2 (PTX2, maximum 61 μg/kg). Oysters also contained OA and PTX2, but always below the MPL. Toxin content per cell measured from phytoplankton concentrates in filters was most likely overestimated (up to 461 pg OA/cell and 668 pg PTX2/cell), but showed an increase of cell toxicity towards the end of the bloom. OA-diol esters were not detected in phytoplankton aggregates. Concentration of DSP toxins in SPATT devices were up to 94 ng OA/g resin⋅day, 42 ng PTX2/g resin⋅day and 7 ng PTX2-sa/g resin⋅day. The applied monitoring strategy, based on the measurement of Dinophysis cell abundance in the water column, was effective to protect public health and did not extended the regulatory closure unnecessarily. Concentration of DSP in SPATT bags followed Dinophysis abundance dynamics, thus SPATTs were confirmed as a valuable research tool for Dinophysis blooms.