OCCURRENCE AND TOXICOLOGICAL EVALUATION OF CYANOBACTERIAL TOXINS IN ALBERTA LAKES AND FARM DUGOUTS

The occurrence of neuro- and hepatotoxins produced by cyanobacteria (blue-green algae) was assessed in eight lakes and six farm dugouts, located in Alberta. Anatoxin-a, an alkaloid neurotoxin produced by Anabaena flos-aquae, was not detected in the lake blooms with gas chromatography-mass spectrometry (GC-MS). Algal blooms which contained Microcystis aeruginosa almost always had detectable concentrations of microcystin-LR, a peptide hepatotoxin, based on high performance liquid chromatography (HPLC) analyses. Bloom samples from the six farm dugouts contained no detectable quantity of either anatoxin-a or microcystin-LR. However, anatoxin-a and microcystin-LR were detected in algae isolated and subsequently cultured from two separate dugouts. Microcystin-RR was not detected in any bloom sample collected. Among three lakes studied in greater detail, the concentration of microcystin-LR present in the blooms was highly variable between lakes and temporally within each lake over the limited sampling period. Fast atom bombardment-mass spectrometry (FAB-MS) performed on a composite of several bloom samples from one lake confirmed the identity of microcystin-LR. Bioassays were performed with a subset of the bloom samples to determine acute toxicity to mice. Intraperitoneal injection of bloom extracts containing microcystin-LR resulted in a massive dose-dependent pooling of blood in the liver, shock and very rapid (as quickly as 50 min post-injection) death of injected mice.