An Engineered Living Artificial Reef Prototype Constructed with Ceramics, Microalgae, and Hydrogels with Potential for Environmental Restoration.

Aquatic ecosystems are under stress worldwide due to extreme weather, overfishing, and pollution. Restoration approaches, such as the deployment of artificial reefs, are needed to mitigate this environmental stress. Here, we designed and tested a living artificial reef consisting of a solid calcium carbonate ceramic structure inoculated with microalgae embedded in a hydrogel matrix. The calcium carbonate ceramic structure was sintered at temperatures as low as 500 °C without thermal decomposition in air using only 1 wt % lithium fluoride. Hydrogel encapsulation protected the microalgal cells and allowed them to grow and remain attached to the ceramic surface. We show that small-scale prototype living artificial reefs removed 69 and 81% of the phosphorus and nitrogen, respectively, from estuarine water after incubation in the laboratory for 24 h. Future efforts to optimize geometry, increase scale, and demonstrate field deployment will be necessary to develop this technology as a mechanism to restore nutrient-contaminated aquatic ecosystems.