By Abigail Engleman, Florida State University Ph.D. Gradate Student, Advisor Dr. Sandra Brooke- August 2017
Update- April 2018: All settlement units were destroyed in Hurricane Irma, September 2017. The units have since been removed. The project will be repeated Summer 2018. New settlement tiles will also feature embedding chemical morphogens to further enhance larval settlement.
Shortly after sunrise, we loaded boxes of 3D printed coral onto the boat deck, hoping they could survive the painstakingly long ride up north to the research site. I clinched my fists as the boat jumped through the waves. “How are they doing back there, Anthony?” I yelled. “Still surviving,” he shouted. After 90 minutes of anxious anticipation, we arrived at the site and removed the coral tiles from their box. I let out a sigh of relief as I realized, they were all in one piece. These coral replicates had successfully endured their 600-mile journey from Tallahassee to their deployment site in the Florida Keys.
On July 24-28, 2017, 96 settlement tiles and 144 coral replicates were deployed in waters surrounding the Coral Restoration Foundation’s Coral Nursery. The settlement tiles were designed to mimic abiotic characteristics of natural reefs. In three months, they will be removed and assessed to determine if the organic structure of these man-made pieces is enough to fool coral larvae into calling them home, and protect them for long-term recruitment.
Reefs that fall victim to physical disturbance offer limited hard surfaces for new coral larvae to attach to. Deploying ships and other man-made structures is a traditional method of restoring and rehabilitating fully or partially degraded reefs. These man-made structures provide substratum that is otherwise unavailable, which fish and invertebrates use as habitat. The three-dimensional characteristics of these structures are important determinants for which assemblage of species will populate them. Many studies have pinpointed the structural designs necessary to attract economically important fish, but what level of complexity is needed to recruit coral—the reef builders— to a man-made substrate?
To address this question, I designed settlement tiles that mimic the structural complexities found on natural reef environments. These settlement tiles were designed— in collaboration with Florida State University’s High Performance Materials Institute— using 3D modeling software. The 3D model was used to cut a frame for silicone molds, which were used to pour flat settlement tiles and tiles with rows of 1 cm3 crevices. Each tile was created using aragonite sand and neutralized- Portland cement.
A second level of structural complexity was tested by scanning, modeling, and 3D printing coral replicates. These coral replicates were attached to both flat and crevice tiles to assess whether their presence provides additional refuge for increased larval recruitment. Ideally, the small crevices will encourage larval settlement and offer initial protection, while the coral replicate will act to slow down the ambient water flow, provide shading, and further protection against predators. The combination tiles (crevices and 3D coral replicates) will test the synergistic effect of natural reef complexities on coral recruitment.
The tiles were deployed in six units throughout the site. In mid-December, the tiles will be removed and analyzed for size, species, and abundance of coral recruits. These findings will provide insight into optimal artificial substrate design for enhancing coral recruitment and improving large-scale reef restoration efforts.
** All necessary permits were received prior to conducting this research