Abstract

In Quellón Bay and nearby areas, shellfish aquaculture is very relevant, and it is near to the upper border of Alexandrium catenella plague area. Were studied five harmful dinoflagellate species from February 2012 until April 2013, by collecting samples for vegetative cells and cysts abundances estimations, and shellfish for toxicity analysis. Quantitatively Dinophysis acuminata was the most relevant species, but only a pair of shellfish samples were positive using DSP mouse bioassay, attributed to false positives due to presence of yessotoxins and especially pectenotoxins (PTXs), since PTXs have been previously associated to D. acuminata in this region. Two Alexandrium species (A. catenella, A. ostenfeldii) were relevant because of their constant presence, although each reached their maximum relative abundance in different periods. A. catenella, A. ostenfeldii, Protoceratium reticulatum and Lingulodinium polyedrum cysts in sediment traps and bottom samples were identified; but no vegetative cells of L. polyedrum were detected in plankton samples, however during a sampling in 2015, few cells were identified in the studied area. This taxon reached cyst higher estimates, but estimations for all species were very low, confirming that harmful species cysts numbers depend on vegetative cells abundance, and only after an intense bloom they could be detected in significant numbers. Regarding toxicity, only negative results using mouse bioassays for PSP were observed; while by HPLC analysis GTX2-3 traces and GTX4 in subtoxic levels were detected. The source species is not certain, but GTXs could be attributed to A. ostenfeldii.