Revista Chilena de Historia Natural 76 (4): 681-698, 2003
RESEARCH ARTICLE
Spatial and temporal distribution patterns of blooms of Alexandrium catenella
(Whedon & Kofoid) Balech 1985, on inland seas of northwest Patagonia, Chile
The presence of the toxic dinoflagellate Alexandrium catenella was first
recorded during the early 1990s in the fjords and inland seas of the Chilean Northwest Patagonia. In 1995 regular phytoplankton
monitoring programs were initiated with the financial support of different national institutions with the purpose of detecting these toxic
dinoflagellates and assessing their effects on shellfish. During this period, an important but incomplete database was obtained, due
mainly to the different work objectives of each monitoring program. In this paper we review the available data, searching for patterns
that help us to gain insights into the temporal and spatial distribution of A catenella in this region. During the early years
(1995 to 1998) the sampling was undertaken monthly and since later 2000 onwards, samples were taken every week but in fewer
sampling stations. Phytoplankton and shellfish samples were collected in the same stations but these varied in number every year.
From late 1995 to 2002 four toxic algae blooms of A. catenella were recorded with different intensity and distribution
patterns. However, a pattern became apparent when the distribution was expanding northwards (from 45o 47’ S in 1996 to 42o S,
Chiloé in 2002). All four algae blooms recorded were highly seasonal (spanning from January to March) and were correlated with the
highest paralytic shellfish poisoning (PSP) records. We suggest that benthic cyst beds are a very important factor in initiating toxic
dinoflagellate blooms of A. catenella in the fjords and inland seas of southern Chile, whose life cycle shows a biannual
occurrence, possibly due to variations in environmental conditions. This apparent cycle could be a response to oscillations in the
neighbor ocean affecting general circulation patterns as well as water column features (e.g., temperature) of inland seas, favoring or
inhibiting these toxic blooms. Expanding spatial distribution of A. catenella blooms seems to be strongly related to surface
water drift driven by wind forcing as well as by circulation features of inland seas in northwest Patagonia in southern Chile.
Key words:
Alexandrium
catenella, distribution, inland seas, southern Chile
