This study aims to investigate the efficacy of UV-C irradiation supplied with LED technology, with hydrogen peroxide (H 2 O 2 ), individually and in combination, for the inactivation of the harmful microalgae Heterosigma akashiwo and Prorocentrum lima , and changes in okadaic acid production in P. lima . The results revealed different sensitivity of both species, being P. lima more resistant to H 2 O 2 ( EC 50 = 21.30 mg L -1 ) with respect to H. akashiwo ( EC 50 = 6.67 mg L -1 ). The UV treatment at 265 and 275 caused similar effect on growth inhibition, although the treatment at 275 caused significantly greater impact on the photosynthetic yield. P. lima was more resistant to the UV treatment at 275 nm ( ED 50 ≈ 189.5 mJ cmL -2 ), with respect to H. akashiwo ( ED 50 ≈ 36.5 mJ cm -2 ). The combined treatment was applied following three strategies: H 2 O 2 followed by UV, UV followed by H 2 O 2 , and simultaneous application of UV + H 2 O 2 . UV + H 2 O 2 application achieved the greatest effects on growth inhibition (82.7% for H. akashiwo and 72.9% for P. lima ) and photosynthetic yield inhibition (44.9% for H. akashiwo and 20.0% for P. lima ), occasionally reaching inhibition levels comparable to those observed under the UV - H 2 O 2 sequential strategy. UV-LED irradiation modulated okadaic acid (OA) production in a wavelength-dependent manner, with 265 nm inducing moderate OA enhancement (up to +21.9%) and 275 nm consistently suppressing OA levels (up to −13.8%), while combined UV/H₂O₂ treatments achieved the strongest OA reduction (−19.2% to −21.8%). Overall, this study provides quantitative evidence to optimize UV-LED/H₂O₂ treatment configurations for the inactivation of resilient marine microalgae, highlighting species-specific responses, wavelength-dependent effects, and the importance of treatment sequencing for effective growth suppression and photosynthetic impairment. • UV-LED/H₂O₂ strategies were assessed using growth and photosynthetic endpoints • Heterosigma akashiwo was more UV- and H₂O₂-sensitive than Prorocentrum lima • Growth inhibition was similar at 265 and 275 nm, but photosynthetic damage was higher at 275 nm • H₂O₂–UV sequencing showed the weakest inactivation performance • Simultaneous and sequential UV - H₂O₂ achieved the highest inhibition levels
Ibáñez-López et al. (Sun,) studied this question.