Spatial and temporal variability of Alexandrium catenella and PSP in southern Chile (43° - 55° S) (May 2006 - July 2010)

Since 1972 Alexandrium catenella and Paralytic Shellfish Poison (PSP) are known from Magellan Strait, being sporadic and restricted to the Magellan region until 1990. Afterwards, recurrent annual blooms and PSP outbreaks and a northern expansion occurred. A. catenella was detected in the Aysen region in 1992 and in 1998 in the southeast of Chiloe Island. In October 2009 it reached its most northern distribution at Calbuco (41°48’S; 73°10’W) and was cited at the Pacific coast of Chiloe Island. The blooms - PSP outbreaks - show different annual patterns encompassing vast geographical areas. In its northern area of distribution, they are sporadic, reaching densities of 1,000 cells l -1 and a toxicity of 1,419 µg STX eq. 100 g -1 shellfish meat. In the southern area, densities have been up to 53,800 cells l -1 , toxicity has reached 27,159 µg, nevertheless the highest densities, 1,132,200 cells l -1 , the highest relative abundances and the greatest mean PSP levels have been observed in the region of Aysen. The interannual variability and its wide geographic coverage, including sectors and periods with higher probabilities to detect the microalga and PSP, suggest that the bloom initiations and PSP outbreaks are of climatic - oceanographic origin.