Blooms of Pseudo-nitzschia pseudodelicatissima and P. calliantha, and associated domoic acid accumulation in shellfish from the South Brazilian coast

The toxigenic diatom Pseudo-nitzschia pseudodelicatissima (Hasle) Hasle is reported for the first time in the south-western Atlantic Ocean, and is associated with high concentrations of domoic acid (DA) in cultivated mussels. Water samples were collected from seven shellfish farms along the coast of Santa Catarina State, South Brazil, from March 2008 to March 2009. The material was identified in transmission electron microscopy, and typical morphological features of the species were presented and compared with data available in the literature. Pseudo-nitzschia pseudodelicatissima appeared in higher abundances during the austral summer of 2009 from 21 January to 17 February, accounting for 80.2-98.0% of the total Pseudo-nitzschia cells in the majority of the stations. Pseudo-nitzschia cells reached abundances as high as 22.5x10(6)cellsL(-1) almost entirely composed of P. pseudodelicatissima. At four stations, blooms lasted 7-15 days, depending on the sampling station. The concentrations of DA measured in the bivalve Perna perna (Linnaeus, 1758) surpassed the threshold value of 20gg(-1) wet weight of tissue for 13 days, with maximum value of 98.5gg(-1), prompting the closure of harvesting and the embargo of shellfish commercialization for 31 days. Other potentially harmful Pseudo-nitzschia species detected during the summer blooms of P. pseudodelicatissima were P. calliantha Lundholm, Moestrup & Hasle, P. multiseries (Hasle) Hasle and P. pungens (Grunow ex Cleve) Hasle. Among these, P. calliantha became the dominant species at one station, contributing 86-98% of total Pseudo-nitzschia cell counts and DA concentrations as high as 14.4gg(-1). In conclusion, P. pseudodelicatissima was recorded in high abundance at 5 of the 50 shellfish farms along the Santa Catarina coastline in 2009, and was associated with high concentrations of DA in mussel tissues. This correlative evidence points to this species as a probable novel threat to commercial shellfish farming and the regional tourism in Santa Catarina State.