OTEC-Assisted Mariculture Integrated with Symbiotic Anemone–Zooxanthellae Systems: A Numerical Investigation for Sustainable Coastal Applications

Coastal regions are under pressure globally due to the complex balance between increasing energy demand, food production, and environmental sustainability. This study presents a numerical model and feasibility analysis of an integrated system that aims to simultaneously reduce the environmental impacts of energy production and marine aquaculture. The proposed model creates a multifunctional circular production concept by combining an Ocean Thermal Energy Conversion (OTEC) system with a fish farming unit and a symbiotic anemone–zooxanthellae-based bioremediation module. The model was developed for the conditions of Turkiye's southeastern Aegean coastline and simulates base load energy production via the Organic Rankine Cycle (ORC) even at low temperature differences, as well as the removal of inorganic nutrients (ammonia, nitrate) from fish farms by the symbiotic system and the release of photosynthetic oxygen into the environment during this process. Based on advection–diffusion–reaction equations, this model combines physical and biological processes within a single computational framework to evaluate the system's thermodynamic efficiency, biomass dynamics, and economic feasibility. The results show that with a depth difference of 40 m and a flow rate of 600 kg/s, approximately 9.96 GWh of energy can be produced annually, with a LCOE of 0.03 USD/kWh and a positive net present value (NPV ≈ 6.8 million USD). Furthermore, it was determined that the system could reduce carbon emissions by up to 4,682 tons of CO2 per year and contribute to eutrophication control through nutrient removal. In this regard, the study presents an applicable model for sustainable coastal development within the scope of blue growth strategies by bringing together energy, food, and environmental components on a single integrated platform.