Abstract

Harmful species of Alexandrium, Dinophysis, Protoceratium and Pseudo-nitzschia, are present in Chilean fjords sometimes in bloom conditions or associated to toxic outbreaks. Data from 2006 to 2013 were analysed to understand the composition, abundance and distribution of the micro-phytoplankton, including harmful species, in the Reloncaví (RF, 42°40’S) and Puyuhuapi fjords (PF, 44°40’S) and Union channel (UC, 52°00’S). Diatoms contributed not less 98% of total cell density, with Skeletonema spp., contributing from North to South with 90, 39 and 28% of total density. The harmful species were numerically subordinate (<1% of total number), with the exception of Pseudo-nitzschia cf. pseudodelicatissima and P. cf. australis that both contributed 45% of total density in PF. Both species were present in low numbers in RF (0.3%) and UC (5.5%). A. catenella, A. ostenfeldii and D. acuta were absent in RF; these species plus D. acuminata and P. reticulatum were present in the other two sectors. The studied areas span climatic and oceanographic differences due to their latitudinal position and local land-sea interactions (e.g. river inputs and glacier melting), that determine differences in composition and density of total micro-phytoplankton, including dissimilarities in composition and abundance of harmful species