Effects of Harmful Algal Bloom of Alexandrium catenella in the mass mortality of the surf clam Mesodesma donacium in Chiloé Island, Chile

In late February 2016, a HAB of A. catenella was detected in Southern Chile leading to the banning of shellfish harvesting in an extended geographical area. In May 1, 2016 this bloom produced a massive beaching of surf clams... [ view full abstract ]

In late February 2016, a HAB of A. catenella was detected in Southern Chile leading to the banning of shellfish harvesting in an extended geographical area. In May 1, 2016 this bloom produced a massive beaching of surf clams M. donacium in Cucao, Chiloé. The impacts caused leaded the community of affected areas to link the shellfish mortality with the pollution produced by salmon aquaculture and not to the noxious effects of HAB. Consequently, massive protests against the salmon industry and the Chilean government were developed along the country. To determine the effect of PSP toxins in M. donacium, samples were taken in Cucao three days after the mass mortality. Individuals were dissected in digestive gland (DG), foot (FT), adductor muscle (MU) and other body fractions (OBF) and histopathological and toxin analyses were carried out. Analyses did not show any damage in tissues. The toxicity ranged from 10000 to 104000 μg STX equivalents/kg, with the toxin profile dominated by GTX3, GTX2, GTX1 and GTX4. The most toxic tissue was DG (22205 μg STX eq/kg), followed by OBF (7111), FT (2943) and MU (314). These results suggest that the mortality was caused by the high concentration of toxins as lower toxicities have been shown to kill or substantially damage other bivalve species. During the sampling period the proportion of shellfish not buried decreased with time, suggesting that some affected individuals can recover from the impact of toxins and bury again.