Cyanotoxins were evaluated in seven water bodies in central Chile (Avendaño, Lo Galindo, Grande de San Pedro, Lanalhue, Vichuquén, Torca, and Llico) from October 2022 to May 2023. Microcystins (MC-RR, MC-YR, MC-LR, MC-LA) and nodularin were quantified by HPLC-DAD, and their relationships with environmental variables and cyanobacterial abundance were assessed using Spearman correlation and principal component analysis (PCA). Cyanotoxins were detected in six systems, with MC-LR as the dominant congener. The highest concentration (407.5 µg/L) occurred in the mesotrophic Laguna Grande de San Pedro. Correlation analysis showed nodularin positively associated with conductivity (ρ = 0.40, p < 0.05), while microcystins were negatively correlated with temperature (ρ to −0.60, p < 0.05). PCA explained 57.7% of variance, distinguishing toxin patterns along gradients of temperature, pH, conductivity, and N:P ratio. Cyanotoxin occurrence was weakly related to cyanobacterial abundance but consistently associated with low N:P ratios. These findings confirm the presence of cyanotoxin-producing strains in the studied water bodies and highlight the need to integrate nutrient dynamics, cyanobacterial community structure, and multi-congener toxin analysis into monitoring programs. Furthermore, the results demonstrate that mesotrophic systems could represent emerging sources of cyanotoxin production, underscoring the need to improve risk assessment and management strategies.
Beltrán et al. (Wed,) studied this question.