Occurrence of multiple cyanotoxins in Alentejo freshwater reservoirs (South of Portugal): First report of cylindrospermopsin and anatoxin-a

This study investigated cyanotoxin co-occurrence in interconnected water reservoirs in Southern Portugal. LC–MS/MS analysis of 69 samples confirmed the presence of microcystin-LR, microcystin-RR, cylindrospermopsin and anatoxin-a, with maximum concentrations of 1.90, 0.35, 0.69 and 0.53 μg L -1 , respectively. Toxins co-occurred and showed distinct spatial profiles. This is the first report of cylindrospermopsin and anatoxin-a in the Alqueva system. Saxitoxin was detected qualitatively, and nodularin was not detected. Microcystin-LR was present at the highest measured concentration, while toxin co-occurrence reinforces the need for monitoring multiple cyanotoxins.