Arcilla, Keibriel Keill P.2026-09-122026-09-122025-05Arcilla, K.K.P. (2025). Efficacy of ethanolic extract derived from Phaeophyta (Turbinaria ornata) against Aeromonas hydrophila and Staphylococcus aureus. [Unpublished Master's Thesis]. Don Mariano Marcos Memorial State University – South La Union Campus, Agoo, La Union. Lakasa ti Sirib, DMMMSU Institutional Repository.https://lakasa.dmmmsu.edu.ph/handle/123456789/2527Abstract OnlyThe research examined the phytochemical profile and the in vivo antimicrobial activity of the ethanolic extract of Turbinaria ornata against Aeromonas hydrophila and Staphylococcus aureus. Phytochemical screening demonstrated the existence of bioactive principles, including alkaloids, terpenoids, tannins, flavonoids, steroids, and saponins, that further proved the medical potential of T. ornata. The levels of TPC and TFC were considerable for antioxidant activities. Antimicrobial assays demonstrated that the T. ornata extract inhibited A. hydrophila and S. aureus, with dose-dependent curves. For range finder test, the results showed that higher concentrations of the extract (50%, 75%, and 100%) exhibited the most significant antimicrobial activity. The study also measured the specificity of the extract at various concentrations, which showed that increasing the concentration improved the extract's specificity against both pathogens, with Treatment III (45%) and Treatment 1V (75%) being most effective. Higher extract concentrations showed increased inhibition zones, although the bacteria showed resistance at lower concentrations. Survival in fish upon infection by the bacteria was significantly improved in Oreochromis niloticus fingerlings by the vivo trials. Higher concentrations of the extract immersed in the fish improved survival because of the extract's immunostimulatory and antibacterial effects. These findings present T. ornata as a promising natural antimicrobial and antioxidant agent with potential applications in aquaculture disease management and pharmaceutical development. Further studies on bioactive compound isolation and mechanism of action are recommended to optimize its therapeutic potential.enThesis