The long-term exposure of cyanotoxin, cylindrospermopsin, on the macrophyte Lemna trisulca

ABSTRACT

The increase in frequency and prevalence of cylindrospermopsin (CYN)-producing cyanobacteria blooms have become a growing problem worldwide. Therefore, the long-term effects of CYN on the physiological processes of the macrophyte, Lemna trisulca, were examined. During a 5-day exposure to a range of CYN concentrations (0.5, 1 and 5 μg ml⁻¹), the low levels of stress experienced by L. trisulca stimulated its growth rate and photosynthesis and led to an increase in the synthesis of photosynthetic pigments. In turn, it was shown that a 3-week exposure to the highest tested CYN concentration (5 μg ml⁻¹) resulted in the inhibition of biomass accumulation (by 7.6%) compared with that of the control plants, but necrosis and chlorosis were not observed. A negative correlation with the concentration of carotenoids was also observed, which may suggest that the antioxidant mechanisms of L. trisulca are effective only up to a certain CYN concentration. An increase in protein content in the tissues of macrophytes treated with concentrations of CYN ranging from 0.5 to 5 μg ml⁻¹ indicates that the toxin did not inhibit protein synthesis but increased the metabolism of L. trisulca, potentially to provide energy for defence. The toxin also affects the homeostasis of mineral ions in cells. This is the first description of the physiological response of L. trisulca to the long-term effects of a wide range of CYN concentrations.

KEYWORDS:

• Cyanobacteria
• fresh water
• Raphidiopsis raciborskii
• toxicity

Acknowledgements

We are grateful to Professor Zbigniew Lechowski for his constructive helpful comments and assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary materials

The following supplementary material is accessible via the Supplementary Content tab on the article’s online page at https://doi.org/10.1080/09670262.2021.2014982

Supplementary fig. S1. HPLC chromatogram of the extract obtained from Raphidiopsis raciborskii CS-505/7 at λ = 263 nm

Supplementary fig. S2. HPLC chromatograms at λ = 263 nm of (A) purchased CYN standard, (B) CYN purified from the material cultivated in laboratory conditions.

Supplementary fig. S3. UPLC chromatogram of the obtained CYN at 263 nm.

Supplementary fig. S4. ESI-MS spectrum of the obtained CYN; m/z 416 [M+H]⁺.

Supplementary table S1. Two-way ANOVA results on the influence of CYN concentration, exposure day and interaction between CYN concentration and exposure day on biomass accumulation, photosynthesis and respiration rate, photosynthetic pigments and protein content.

Supplementary table S2. One-way ANOVA results on the influence of CYN concentration on the concentration of ions in the media, membrane damage and MDA content.

Additional information

Funding

This work was partially supported by the National Science Centre (NCN), Poland [grant number 2016/23/B/NZ9/01041].