Paralytic shellfish toxins in the freshwater cyanobacterium Aphanizomenon flos-aquae, isolated from Montargil reservoir, Portugal

Montargil reservoir, located in a dry flat area in the centre of Portugal, was filled in 1958 to fulfil agricultural, electric and industrial requirem ents. In May 1996, an intensive bloom of phytoplankton was detected, The al gal community was strongly dominated by cyanobacteria with predominance of Aphanizomenon flos-aquae from May to June and Microcystis aeruginosa from J uly to August. Extracts of samples collected during the bloom period showed high toxicity by mouse bioassay. During the M, aeruginosa predominance per iod, the toxicity was ascribed to the presence of hepatotoxins, but clear s ymptoms of paralytic shellfish poison were observed when A. flos-aquae was the dominant species. In order to confirm the production of neurotoxins a s train of A, flos-aquae was isolated and established in culture, In this man uscript, we show the morphological characteristics and confirm paralytic sh ellfish toxins production by the strain isolated and maintained in culture. Identification of the saxitoxin analogs was achieved using highperformance liquid chromatography with postcolumn fluorescence derivatization (HPLC-FL D) and liquid chromatographic mass spectrometry technique (LC-MS). The toxi ns found in the culture extract were GTX5 (64.5 mol%), neoSTX (23.0 mol%). dcSTX (6.1 mol%), STX (5.4 mol%) and GTX6 (1.1 mol%). This is, to our knowl edge, the first report of unambiguous evidence of paralytic shellfish toxin s produced by freshwater cyanobacteria in Portugal. The toxin profile is ra ther different from the previously reported PSP producing A. flos-aquae and demonstrates its diversity in terms of toxin production. (C) 2000 Elsevier Science Ltd. All rights reserved.