Paper: Ruhl EJ, Dixson DL (2019) 3D printed objects do not impact the behavior of a coral- associated damselfish or survival of a settling stony coral. PLoS ONE 14(8): e0221157. https:// doi.org/10.1371/journal.pone.0221157
Coral reefs are amazing staples to diverse and complex ecosystems, and sustain over 25% of all marine life. However, the same reefs which support so much in the ocean are also incredibly vulnerable to climate change, and are facing extreme danger. As one of the world’s largest carbon sinks, the ocean sucks up a massive portion of the influx of carbon dioxide characteristic of climate change. All of this excess CO2 throws our ocean off balance, quickly and drastically warming its waters and increasing its acidity. These climate change-byproducts have caused many of the world’s integral coral reefs to bleach (for more on the process of coral bleaching & the effects of ocean acidification, check out this piece on interspecific coral hybridization). As our ocean warms at a rate faster than anyone expected, coral reefs are facing an absolutely massive threat, which puts the many organisms which depend on them at great risk.
In the face of mass bleaching and other anthropogenic (human induced) stressors, researchers and scientists alike have been working on ways to both bolster coral reef growth and study coral reef environments without disrupting them – and artificial reef construction has been one technique used to do so. In fact, 3D printing holds many advantages in creating precise replicas of species, stimuli, or habitats due to its ease of use, relative low cost, and accessibility. Scientists can use 3D printing to study organism behavior which may be too challenging or disruptive to examine in the field and create new, innovative management strategies that can help protect delicate, threatened coral reef ecosystems.
However, before the use of 3D models in the field, scientists need to determine whether or not these artificial constructions are harmful to the coral they aim to support or stress the marine organisms they intend to study. In order to explore whether 3D printing should continue to be a viable method of artificial reef construction, Ruhl & Dixson (2019) test how reef organisms react to both 3D printed and natural coral skeletons.
Many species of fish, like damselfish, have a symbiotic relationship to coral species. Additionally, coral spats (settled group of coral spawn) need substrate to attach to. Ruhl and Dixson (2019) create 3D printed settlement tiles to mimic textured substrate, and pick two species of coral skeleton to use in both printed and natural form: Acropora formosa, coral with long, wide set branches, and Pocillopora damicornis, a bushy coral. According to these coral species’ environments, the researchers then acquired 60 blue-green chromis (Chromis viridis) and collected 42 spawning adult colonies of Caribbean mustard hill coral (Porites asteroids) to see how each would react to the natural and 3D printed coral skeletons respectively.
The researchers tested the blue-green chromis’ behavior by placing them in tanks with four 3D printed coral skeletons (differentiated by filament treatments, or the material the print is created with) and one natural coral skeleton, all of the same species. By including five total skeletons, Ruhl and Dixson (2019) could determine if the artificial skeletons created an environmental stressor. They then monitored the chromis to detect whether they would maintain typical reef behavior, such as the ability to seek refuge within the protection of the skeleton. The blue-green chromis showed no significant preference between the A. formosa and P. damicornis skeletons, which indicated that these damselfish did not make any choices based on the appearance and structure of the corals. Additionally, the blue-green chromis showed no significant preference between the natural and 3D printed coral skeletons, exhibiting no behavior that the scientists could classify as different than their behavior with natural coral skeleton. Unaffected activity level, behaviors, and preferences suggest that the artificial coral skeletons did not negatively affect tested blue-green chromis, and that use of 3D printed coral skeleton can be comparably useful and relatively low risk in field research.
Next, Ruhl and Dixson (2019) used printed textured substrate tiles to see how well Caribbean mustard hill coral spawn would settle. They found that 3D printed tiles had significantly higher settlement than no tiles or substrate, which suggests that these tiles were successful in mimicking the natural substrate the coral has shown to prefer and might be similarly productive in the field.
There is one limitation to consider regarding the differences between lab-based research and field-based research. Ruhl and Dixson (2019) explain that scientists should expect higher mortality rates from field research as compared to their lab experiment. Organisms, like the studied newly settled coral, are extremely vulnerable to predation and other environmental and anthropogenic stressors.
Nonetheless, Ruhl and Dixson’s (2019) results indicate that 3D printing is a relatively low risk tool for artificial reef construction that will aid scientists in studying complex coral reef ecosystems and help rebuild damaged reef systems as well. This technique will help scientists continue to understand fragile coral reef environments and work towards protecting and managing them under the various threats they face.
Rishya is a multimedia science communicator with an MS in Media Advocacy from Northeastern University, specializing in Environmental Science Communications and Policy. She spent a year in informal education and policy advocacy at the New England Aquarium as an Educator and at Save the Harbor/Save the Bay as their Communications and Public Relations Coordinator. She also interned for PBS science series, NOVA and was awarded a 2019 Rapport Public Policy Fellowship, which she served at the Massachusetts Division of Marine Fisheries. Rishya’s areas of focus are environmental science, marine science, climate change…and video games!