Le Verge-Campion T. auteur aut IRD Jauffrais T. auteur aut IRD Lefeuvre L. auteur aut IRD Houlbrèque Fanny auteur aut IRD text journalArticle eng text/pdf reformatted digital access Arthrospira platensis extract is incorporated into sunscreen formulations for its beneficial and UV-protective properties on cultured human cells. However, its effects have not yet been assessed on non-target organisms such as endosymbiotic microalgae in coral tissue. To evaluate its effects, we investigated the photophysiology of the cultured dinoflagellate Cladocopium goreaui using PAM fluorometry (RLC, OJIP) after a 5-day exposure to different extract concentrations. Our results show that, through a hormetic effect, A. platensis enhances the performance index (Pi_Abs) at 0.018 mg L-1 by increasing the number of active reaction centers (RC/ABS) and improving electron transfer efficiency (phi Eo, psi Eo) along the electron transport chain. Conversely, beyond 108.8 mg L-1, negative impacts appear on PSII, increasing the apparent antenna size (ABS/RC) and impairing the oxygen-evolving complex (K-peak), ultimately reducing the maximum relative electron transport rate (rETRm). This relative toxicity, obtained only for the highest concentrations, supports its potential incorporation into cosmetic formulations. This study contributes to improving the ecotoxicity assessment of cosmetic products on non-target organisms. specialized Arthrospira platensis Cladocopium goreaui photophysiology dose-response relationship JIP-test coral PACIFIQUE 034 084 035 5 3 50 [16 p.] 2025 https://www.documentation.ird.fr/hor/fdi:010095039 10.3390/phycology5030050 [F B010095039] https://www.documentation.ird.fr/hor/fdi:010095039 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2025-11/010095039.pdf IRD - Base Horizon / Pleins textes 2025-11-18 2025-11-18 fdi:010095039 fre