Abstract

Pseudo-nitzschia blooms and the presence of domoic acid (DA) in shellfish have been poorly characterized in the Sub-Antarctic Ecoregion of the South Pacific. Here, we present the space-time distribution of Pseudo-nitzschia spp. in the northern area of the Magellan region (49-52° S), distributed over a period of 10 years, using a monthly sampling frequency, from May 2006 to December 2017. The identification of the complexes was carried out with light and scanning electron microscopy, identifying five species of the genus Pseudo-nitzschia belonging to the seriata and delicatissima complex. There was an increase in abundance (100 and 2.660.700 cells L-1 at the beginning and end of the study period, respectively) and the recurrence of these two complexes over the years, with their distribution and associated relative contribution to two water mass present in the study area: Subantarctic Surface Water (Subantarctic Mode Water or SAMW) and Brackish Estuarine Water (BEW). A predominance of the P. seriata complex was observed, mainly during the winter months characterized by the input of SAMW into the system of fjords and channels with low temperatures (6-8 °C) and high salinity (30 to 33). Conversely, P. delicatissima complex was associated with the BEW, which increases its presence between the summer months, when a high input of freshwater cause’s stratification in the water column associated to relatively higher temperatures (10-12 °C) and lower salinities (26-27).