Acute toxicity of neurotoxin-producing Raphidiopsis (Cylindrospermopsis) raciborskii ITEP-A1 (Cyanobacteria) on the neotropical cladoceran Macrothrix spinosa

Abstract

Cyanobacterial blooms are recurrent phenomena in several water bodies, mostly eutrophic. They are considered a public health problem, especially considering harmful species like Raphidiopsis raciborskii, a bloom-forming cyanobacteria recorded as a producer of neurotoxic and cytotoxic alkaloids. The present study aimed to assess the acute toxicity of a saxitoxin-producing strain Raphidiopsis raciborskii ITEP-A1 on the zooplankter Macrothrix spinosa. Cladoceran clones isolated from an eutrophic system with cyanobacterial blooms records and an oligotrophic one with no bloom record; both from Pernambuco (Northeastern Brazil), were tested for R. raciborskii ITEP-A1 toxicity. Acute toxicity assays were carried out with newborns (<24h, n=10) and the animals were exposed to three concentrations of cyanobacterial cell biomass (μgC L-1). Quantification of saxitoxins (STX and neoSTX) was done by high-performance liquid chromatography coupled with fluorescence detector (HPLC-RF). The EC50(48h) for the Duas Unas and Prata clones were 359 and 189 μgC L-1, respectively. Obtained results showed that M. spinosa Prata was more sensitive to R. raciborskii than Duas Unas, reinforcing the importance of analyzing the previous life history of the test organisms regarding their native environments. However, both clones demonstrated high sensitivity to R. raciborskii, which enhances their potential for biomonitoring toxic cyanobacterial blooms in tropical reservoirs.