Alexandrium catenella cyst accumulation by passive and active dispersal agents: Implications for the potential spreading risk in Chilean Patagonian fjords.

The dinoflagellate Alexandrium catenella is responsible for paralytic shellfish poisoning and negative socioeconomic impacts on the fishing industry and aquaculture. In Chilean Patagonia, the reasons underlying the significant increase in the geographical extension (from south to north) of A. catenella blooms during the last five decades are not well understood. To assess the potential spreading risk of A. catenella during an intense austral summer bloom, we conducted an in situ experiment in a «hotspot» of this dinoflagellate in southern Chile. The objective was to assess the accumulation of A. catenella resting cysts in passive (fishing nets) and active (mussels) dispersal agents during the phase of bloom decline. Large numbers of resting cysts were detected in fishing nets (maximum of 5334 cysts net⁻¹ per month) at 5 m depth and in mussels (maximum of 16 cysts g⁻¹ of digestive gland) near Vergara Island. The potential of these vectors to serve as inoculum sources and the implications of our findings for A. catenella population dynamics are discussed.