Abstract

Since 1972 Alexandrium catenella and Paralytic Shellfish Poison (PSP) along the southernmost Chilean fjords are known and gradually in almost thirty years, have colonized the entire estuarine fjords system (55°-41°S). During the autumn of 2016 have extended its distribution up to 39°S through the Pacific Ocean coastal zone. Besides the geographic expansion, there has been an increase of the frequency and intensity of the A. catenella blooms. The major A. catenella and PSP outbreaks have occurred at the end of the La Niña events but prior to a strong or medium intensity El Niño, excluding 2015-16 event. For the Magellan region time series since 1994 are available of micro-phytoplankton abundance and relative abundance of A. catenella (RA). Were contrasted standardised anomalies of these variables against pluviometry, air and water temperatures and salinity anomalies, through non-parametric correlations, including the Multivariate ENSO Index (MEI). Both biotic variables exhibit significant correlations with MEI, pluviometry, air and water temperatures and salinity standardised anomalies. Moreover, for 1997-98 and 2015-16, the two most intense El Niño of the last twenty years, a striking increase of phytoplankton abundance and RA were observed, but pluviometry, air and water temperatures and salinity showed differential trends. Linkages of micro-phytoplankton abundance and RA through teleconnections to the ENSO it is hypothesized, which are modulated by climatic and oceanographic factors, and an increase of glaciers melting might occur. Results suggest a macro-scale triggering factor regulating the micro-phytoplankton and A. catenella distributions and abundances, but later local factors would regulate these biotic variables.