First report and toxicological assessment of the cyanobacterium Cylindrospermopsis raciborskii from Portuguese freshwaters

The freshwater cyanobacterium Cylindrospermopsis raciborskii has become increasingly prevalent in freshwaters worldwide. This species is a concern from a water quality perspective due to its known ability to produce a potent hepatotoxic alkaloid cylindrospermopsin, which has been implicated in outbreaks of human sickness and cattle mortality. C. raciborskii strains isolated from Brazil have also been found to produce the highly toxic paralytic shellfish poisons (PSPs). This article reports the toxicity of four strains of C. raciborskii taken from three reservoirs and one river in Portugal, as well as the occurrence of this species in other water bodies used for potable and recreational purposes. All four strains grown in pure culture in the laboratory were found to be toxic in the mouse bioassay at 8–24 h after intraperitoneal administration of single doses ranging from 1337 to 1572 mg kg−1 Histological examination indicated that liver damage was the primary lesion; in addition, there was inflammation in the intestine. HPLC/MS tests for the presence of cylindrospermopsin, microcystins, and PSP toxins were negative. The available evidence suggests that another toxin may be present. This constitutes the first report of toxic C. raciborskii in Europe and draws attention to the need for increased monitoring of this cyanobacterium in water bodies used for potable and recreational purposes.