The ArchiREEF project team has created the world’s first 3D printed artificial reef structure. So far, this is the most sustainable and efficient way to grow new coral reefs and restore the marine ecosystem.
What’s wrong with corals
In 2018, a super typhoon destroyed 80% of the corals in Hoi Ha Wan Bay off Sai Kung Peninsula in Hong Kong. Due to a strong storm with wind speeds reaching 250 km / h, only fragments of coral skeletons remained in place of the reefs. A few coral species have survived, but it will take decades for them to recover to their former state.
Coral reefs are rapidly disappearing from the world’s oceans, in large part due to the effects of global warming, which is increasing the frequency and intensity of storms. In 2016 and 2017 alone, 89% of new corals on the Great Barrier Reef died as a result of bleaching caused by global warming. Without decisive action to combat the climate catastrophe, overfishing and pollution, we will lose 70% to 90% of the world’s remaining coral reefs within the next 20 years.
How can reefs be saved?
A team of marine scientists from the University of Hong Kong and the Swire Institute of Marine Science are testing a unique method of reef restoration as part of the archiREEF project. With the help of a 3D printer and a robotic arm, they created the so-called “reef tiles” – terracotta hexagons – and placed them on the seabed in Hoi Ha Van Bay.
Tiles do not replace reefs, they only serve as a foundation for corals and encourage the return of their inhabitants. Terracotta is harmless to the ocean – it is similar to calcium carbonate, which is found in real coral reefs. And most importantly, terracotta clay naturally breaks down: scientists hope that in a few decades, the tile will disappear, and only new corals will remain in its place.
The reef tile design provides a structurally complex base so that coral fragments can find many nooks and crannies to gain a foothold. This prevents the buildup of sediment, which scientists say poses a serious threat to marine life.
The first results of the experiment can be called promising. The survival rate of corals and other inhabitants was 98%, which is 4 times more than with conventional methods.
“It is encouraging that small fish and crabs take refuge in the tile almost as soon as it touches the seafloor,” says David Baker, director of the Swire Marine Science Institute. “I hope the government will allow us to plant reef patches that will contribute to Hong Kong’s coral growth, important biodiversity hotspots, and enjoyable dive sites over the course of my lifetime.”
Why 3D printing
Now 128 hexagonal tiles cover only 40 square meters. m. of the bottom, but if the experiment works, this practice can be scaled up. The idea of terracotta tiles is being tested all over the world: scientists are working on reef restoration in the Maldives, where the largest 3D-printed reef is located, as well as in France and the Caribbean.
Other artificial methods of saving coral reefs are also being tested. In a practice known as “rigs to the reefs”, decommissioned offshore oil rigs have been turned into artificial reefs in the US, Brunei and Malaysia. Deliberate flooding of “used out” ships is another method. The sunken US aircraft carrier USS Oriskany is considered the largest artificial reef in the world, and the aircraft carrier, nicknamed the “Great Carrier Reef”, sunk in northwest Florida in 2006, is one of the most popular diving sites in the United States.
The Hong Kong team, however, believes that using terracotta is much more efficient and safer than other artificial reef building methods. “Concrete contains cement, which is very corrosive,” Baker says. “In seawater, it maintains a very high pH at the surface, which is detrimental to many types of marine species. In addition, concrete structures often appear strangely devoid of life or become covered in an unsightly biofilm of algae, much of which does not support corals or other marine life.”
Modern technologies, in particular, the possibilities of 3D printing, create the conditions for revolutionary solutions in ecology. According to Virko Yu, co-founder and CEO of archiREEF, there are two reasons to use 3D printing:
“The first is adaptability. We wanted to create something that could adapt to any type of coral anywhere in the world. The design we have now is based on an algorithm, and changing the parameters allows you to change the design a bit. Since we see the restoration of corals anywhere as the ultimate goal, design flexibility is critical and 3D printing makes that possible.”
Another reason is the increased complexity and detail of 3D printing compared to traditional molding. There are microorganisms in Hong Kong that need small and complex structures as a refuge. With a 3D printer, you can create structures with much more detail, which is very important for biodiversity restoration. The creators of the project dream of making this technology easy to implement, accessible and popular not only for the circle of narrow specialists, but also for ordinary people.
Virko Yu:
“When we first got the attention of the world media, we started getting messages from people from different countries asking if they could help and do the same on the reefs in their region. And I realized that coral restoration concerns everyone. We want it to be as easy as planting trees – easy and affordable.”
What is the difficulty
Despite the promising idea of archiREEF, most scientists emphasize that no artificial reef technology can be a panacea for the decline of coral reefs.
“3D printing can really help create small, complex substrates on which to house and grow coral larvae,” says Alasdair Edwards, professor of coral reef ecology at Newcastle University. “But given that over the past 50 years, several tens of thousands of square kilometers of reefs around the world have already been destroyed, 3D printing is clearly not a solution, but may play a secondary role. The only solution is to limit greenhouse gas emissions.”