Leveraging Artificial Oxygenation Efficacy for Coastal Hypoxia by Taking Advantage of Local Hydrodynamics

This study evaluates deployment strategies for artificial oxygenation devices to mitigate coastal hypoxia, particularly in mariculture regions. Focusing on a typical mariculture region in the coastal waters of China, we examined the combined effects of topography, hydrodynamics, and biogeochemical processes. A high-resolution three-dimensional physical-biogeochemical coupled model, validated against observational data from three summer cruises in 2020, accurately captured key drivers of hypoxia. Results reveal that hypoxic zones exhibit an uneven distribution, driven by persistent offshore jets at specific locations. Nearshore deployment of oxygenation devices upstream of hypoxic zones significantly improves oxygen delivery and is more cost-efficient due to reduced construction and maintenance requirements. Uncertainty analysis explored the impacts of varying water mass properties, oxygen concentration, injection flow rates, and biogeochemical content. The influence varies depending on the deployment site. Particularly, buoyant plumes can notably reduce the effectiveness of hypoxia mitigation. Artificial oxygenation may lead to unintended ecological impacts, including increased nutrient release and enhanced primary production, which can prolong the duration of hypoxia. Furthermore, simulations indicate that natural downwelling currents are insufficient to transport oxygen-enriched surface water to the bottom hypoxic zones. These findings underscore the importance of comprehensive predeployment assessments and the advancement of oxygenation technologies to ensure both immediate effectiveness and long-term ecological sustainability.