Paralytic shellfish toxins in the Atlantic horse mackerel (Trachurus trachurus) over a bloom of Gymnodinium catenatum: the prevalence of decarbamoylsaxitoxin in the marine food web

This study reports the accumulation of paralytic shellfish toxins (PSTs) in Atlantic horse mackerel (Trachurus trachurus) over a bloom of the toxigenic dinoflagellate Gymnodinium catenatum. High levels of toxins, up to 4800 μg STXeq kg–1, were registered at the peak of the bloom (5.0 103 cells l–1). The suite of individual PSTs was examined. Decarbamoylsaxitoxin (dcSTX) and B1 constituted nearly 90% of toxins (on a molar basis) determined in mackerel. This profile of toxins markedly differs from the known profile of toxins produced by G. catenatum strains isolated from the Portuguese coast, which is dominated by N-sulfocarbamoyl toxins, in particular the C1+2 toxins. The prevalence of the potent dcSTX in the pelagic environment and its transfer through the marine food web is highlighted in this study. Atlantic horse mackerel is identified as a high potential vector of PSTs along the Portuguese coast. This fish species has a central position in the marine food web, being an important predator of zooplankton and at the same time an important diet item of top predators. This study reveals bioaccumulation values that are important for evaluating potential impacts of blooms of PST-producing dinoflagellates on marine ecosystems or their components, such as fish.