Albuquerque Maria Virgínia da Conceição, de Sousa Tales Abreu Tavares, Dias Joelma, Ramos Railson de Oliveira, Leite Valderi Duarte, Lopes Wilton Silva
Department of Sanitary and Environmental Engineering, State University of Paraíba (UEPB), 58429-500, Campina Grande, Paraíba, Brazil.
Department of Sanitary and Environmental Engineering, State University of Paraíba (UEPB), 58429-500, Campina Grande, Paraíba, Brazil.
Toxicon. 2025 Oct;265:108494. doi: 10.1016/j.toxicon.2025.108494. Epub 2025 Jul 11.
The application of advanced oxidative processes has proven highly effective for treating eutrophic waters by degrading cyanotoxins and reducing toxicity. However, many studies evaluate treatment efficacy solely based on reductions in toxin concentrations, often overlooking the potential toxicity of the formed by-products. This study evaluated the phytotoxic effects of cyanotoxin lysate extracts from eutrophic environments on Lactuca sativa L. seed germination, hypocotyl growth, and radicle elongation, as well as the phytotoxicity of microcystin-LR (MC-LR) by-products formed through Fenton process. Cyanotoxin concentrations of 5.0, 2.05, 0.61, and 1.42 μg.L for MC-LR, SXT, anatoxin-a (ATX-A), and cylindrospermopsin (CYN), respectively, were tested at nine dilution levels: 100 %, 75 %, 50 %, 25 %, 12.5 %, 6.25 %, 3.12 %, 1.56 %, and 0 % (control condition). Fenton oxidation experiments were conducted using jar test equipment, with Fe:HO molar ratio of 1:3 and Fe concentrations ranging from 5.0 to 20 mM across treatments (T1-T5). Results confirmed that ATX-A, CYN and MC-LR stimulated the antioxidant system while significantly impairing seedling development, notably inhibiting germination, radicle elongation, and hypocotyl growth. Phytotoxicity effects varied considerably among cyanotoxin samples and Fenton treatments. Notably, contrary to initial hypothesis, lysed extracts of cyanotoxin-producing strains induced lower toxicity than the by-products formed during the Fenton-mediated degradation of MC-LR. These findings underscore the uniqueness of the present study, given the limited number of publications that apply this specific phytotoxicity analysis. Furthermore, they emphasize the need for a comprehensive evaluation of oxidative treatments, taking into account both their degradation efficiency and the potential toxicity of the resulting by-products.
