Given increasing demand for freshwater, seawater reverse osmosis (SWRO) plants are becoming an emergent solution for worldwide water security. However, impacts of brine discharge from the desalination process on Red Sea coral species remain poorly studied. To better understand this, we performed a pre-construction risk assessment of a simulated brine effluent on two Red Sea model corals Acropora sp. and Stylophora pistillata. Physiological parameters and biochemical markers related to corals' oxidative status (cellular damage, antioxidant defenses), redox balance and energy reserves' content were assessed to investigate the potential impacts of elevated salinity on the fitness of coral species. Associated with tissue loss, log-logistic regression models showed lethal concentrations (LC10) thresholds of 19.6 % (≈32 % dilution) and 12.8 % (≈36 % dilution) above ambient salinity for Acropora sp. and S. pistillata. This was accompanied by reduced chlorophyll a and c2, indicating severe stress. Additionally, both species exhibited decreased antioxidant capacity, lower lipid peroxidation levels and loss of redox homeostasis, with S. pistillata showing sensitivity to salinity 22.5 % above ambient (≈30 % dilution). Our findings underscore the vulnerability of these corals to elevated salinity, particularly near desalination plants discharge points. To mitigate these ecological risks, we recommend that hydrodynamic models and habitat mapping be integrated into the planning and design of discharge sites to minimize coral exposure to salinity exceeding 12.8 % (LC10). Implementing a long-term in-situ monitoring program is essential for understanding the full impact of brine discharge over time, ensuring that water security efforts align with environmental conservation goals.