Toxinas paralizantes en moluscos bivalvos durante una proliferación de Gymnodinium catenatum Graham en la Bahía de La Paz, México

From February to March 2007 a harmful algae bloom of Gymnodinium catenatum Graham ocurred in Bahia de La Paz, Mexico, with cell densities from 6 × 105 to 2,39 × 106 cells L^-1. During this event the toxin concentration and toxin profile of paralytic shellfish toxins in mollusks (Pinna rugosa, Modiolus capax, Megapitaria squalida, Periglypta multicostata, Dosinia ponderosa, and Megapitaria aurantiaca), and in phytoplankton samples were determined. Some physicochemical data were obtained. The average values of the surface temperature and dissolved oxygen were 20.9 ± 0.7 °C and 6.9 ± 0.3 mg L^-1. The average concentrations of nitrites, nitrates, ammonium, phosphates, and silicates were 0.22 ± 0.05, 1.04 ± 0.33, 0.89 ± 0.88, 0.81 ± 0.76, and 8.85 ± 1.60 μM, respectively. The concentration of paralytic shellfish toxins in the net phytoplankton samples varied from 4.32 to 79.60 ng saxitoxin equivalents filter^-1, identifying 8 toxins, the most abundant being C1 and C2. The highest toxin concentration found in mollusks were 31.14, 37.74, and 25.89 μg STXeq 100 g^-1 in M. capax, P. rugosa, and M. aurantiaca, respectively. The variations in the paralytic toxin profile in the different mollusks species are given.