3D-printed coral skeletons kickstarts reef recovery

Coral reefs are among the precious natural resources struggling with environmental degradation, with warming oceans, ocean acidification, disease, overfishing, and other threats destroying reefs. The Great Barrier Reef, for instance, has lost more than half its corals since 1995 due to warmer seas.

Reef restoration efforts tend to employ concrete blocks or metal frames as substrates for new coral growth. This is a slow process that cannot keep up with the rate at which reefs are being destroyed; corals deposit their carbonate skeleton at rate of just millimetres per year. In an effort to speed up coral restoration, researchers from KAUST have been exploring the use of 3D printing to create specialised substrates.

“Coral micro-fragments grow more quickly on our printed or moulded calcium carbonate surfaces that we create for them to grow on, because they don’t need to build a limestone structure underneath,” said Hamed Albalawi, a PhD student and 3D bioprinting expert.

The idea of providing coral with a “head start” is not in itself new. Researchers have previously tested approaches to printing coral support structures. However, most efforts have used synthetic materials.

The KAUST researchers have developed and tested a different approach called 3D CoraPrint; this makes use of an eco-friendly and sustainable calcium carbonate photo-initiated ink that they previously developed. Tests in aquariums have shown that this material is non-toxic and the researchers are planning longer term tests to ensure it is safe to use.

While previous approaches have relied on passive colonisation of support structures, this approach involves attaching coral micro-fragments to the printed skeleton to start the colonisation process. It also incorporates two different printing methods, both beginning with a scanned model of a coral skeleton. In the first method, a structured printed from the model is used to cast a silicon mould, which is then filled with the special ink. In the second method, the support structure is directly printed using the ink.

The two approaches offer complementary advantages. Creating a mould means the structure can be easily and quickly reproduced, but the curing process limits the size of the mould. Direct printing is considerably slower and lower resolution, but it allows for individual customisation and the creation of larger structures.

Zainab Khan, another lead author of the study, commented: “With 3D printing and moulds, we can get both flexibility and mimicry of what’s already going on in nature. The structure and process can be as close as possible to nature. Our goal is to facilitate that.”

A recent Georgia Institute of Technology study on coral reef restoration found a potentially symbiotic relationship between Pacific Ocean coral species, which could point towards more effective reef restorations efforts. The research found that increasing coral richness by “outplanting” a diverse group of coral species together can improve coral growth and survivorship overall. This finding may be especially important in the early stages of reef recovery following large-scale coral loss.