Abstract

The Aysén region (44ºS – 48ºS) is a complex marine area of fjords and channels that receives a very large river discharges and glaciar melting waters forming a extensive estuarine system. In this area, blooms of Alexandrium catenella are recurrent events, resulting in paralytic shellfish poison (PSP) outbreaks every summer. Over 10 years (2006 – 2016) observations of cells abundance, flow rivers, hydrographic sections (temperature, salinity and density) and meteorological data (velocity and wind direction, pressure, radiation, air temperature) were used to assess drivers of A. catenella spatial and temporal variability. We hypothesize that the estuarine systems play an important role in cells accumulations due the determination of convergences zones formed by oceanic salty waters and freshwaters. From each sampling year a multivariate statistical approach was used to investigate the samples stations with high values of A. catenella abundance and PSP levels. Additionaly, historical river data flows (Palena, Cisnes and Aysén) were used to determine the high probability periods associated to stratified waters. Water column stability estimations within and outside the frontal region were determined to compare the different stations. The cluster analysis results indicated the stations with the highest abundances and PSP levels were associated to the Moraleda channel, with important temporal and spatial differences linked to river flow anomalies during 2009. We discuss that the dominant factors controlling the A. catenella blooms in the Aysén region were the water column stratification, which regulates the vertical and horizontal distribution along to the Moraleda channel.