Abstract

Temporal distribution of the phytoplankton in a fixed station inside Aysén fjord is described using 130 qualitative phytoplankton samples and water surface temperature measurements taken every 15 days from February 1993 till June 1998. During the analysis a total of 106 species and varieties were identified: 74 corresponding to diatoms, 30 to dinoflagellates and 2 to silicoflagellates, being from marine neritical and oceanic, estuarine, continental and benthic habitats. Between the taxa identified we can oint out three species related to toxin production: Alexandrium catenella (PSP), Dinophysis acuta and D. acuminata (DSP), and several other taxa which affect the salmon industry. Phytoplankton was characterised by the predominance of low salinity diatoms over the other groups with periods in which species characteristic of oceanic waters appear. Therefore the diatoms present as bioindicators of the types of water in the fjord were used. This evidence demostrates that the phytoplankton within the fjord does not follow standard population successions, but reflects an alternation between invasions of species of continental and marine waters to the estuarine environment at the head of the fjord. The water surface temperature presented normal annual fluctuations for a cold temperate region, with extreme values of 5,2° and 16,2°C, with the lowest during 1996 and the highest in 1994 and 1998. The warmer years recording a high persistence of toxic species.