A research team at the University of Hong Kong has created the first 3D-printed terracotta “reef tiles” to help restore eroding coral communities on Hong Kong seabeds. The first clay tiles were placed on the seafloor at Hoi Ha Wan Marine Park in Sai Kung during a week-long deployment exercise in mid-July.

The experiment consists of installing 128 reef tiles, covering roughly 40 square metres in total, at three sites of coral disintegration within the marine park. Led by a team of three marine scientists from the Swire Institute of Marine Science and four architects from the Faculty of Architecture’s Robotic Fabrication Lab, the development of the pilot project began in 2016.

Photo: Agriculture, Fisheries and Conservation Department

One of the three sites, in an area called Moon Island, had deteriorated so much that its coral communities had transformed into sand. Concerned by the severe degradation of the Hong Kong’s reefs, the researchers wanted to create a “substrate that can facilitate coral restoration, while conserving the local biodiversity,” Vriko Yu, a Ph.D. student involved in the project, told HKFP.

Designed to mimic the natural shape of brain coral, the team designed the hexagonal tiles with clay to minimise any artificial impact on the ocean’s biodiversity: “Our hope is that the our planted corals can become big enough to stabilise themselves and form a natural habitat,” Yu said. The team said it hopes that the environmentally-friendly terracotta tiles will erode and disappear into the seafloor when they are no longer needed.

A coral restoration clay tile. Photo: Vriko Yu

The tiles have also been specifically designed for the unique conditions of Hong Kong waters, where coral reefs have been slowly disappearing as the result of decades of neglect. Reefs have also faced harmful factors such as long-term water pollution, overfishing, bioerosion, and excessive sedimentation. This, in turn, has led to a gradual collapse of local marine ecosystems.

Hong Kong’s ‘super-coral’

In the global context, Hong Kong waters make for a compelling study for marine scientists, as it is one of the harshest environments for coral to thrive in. Coral that can grow in Hong Kong waters are dubbed “super-coral.”

“Hong Kong is not an easy place for coral …The water quality has improved a lot over the last decade which had given us one important condition to keep the corals healthy. However, there are some external factors like red tides and typhoons which could take away our efforts in a blink of an eye,” Yu told HKFP.

Coral is not only indispensable to efforts to restore marine life in Hong Kong waters, it also provides the basic habitats for sea creatures such as invertebrates and small fish. In addition, reefs are an important factor in the fight against climate change.

Photo: Agriculture, Fisheries and Conservation Department

“I like to use the analogy of Jenga. The more blocks you have together, the less likely it will be to collapse. That’s why the best strategy against climate change is to create as much as we can, to encourage as must biodiversity as we can,” Yu explains.

As the project develops, the team will monitor the sites quarterly, collecting data on the amount of coral that have taken to the tiles, and the biodiversity levels within the developing reefs.

Although in its early stages, the project’s success will be a positive step in marine preservation efforts internationally. Yu says she hopes the project’s success will encourage other cities to also preserve and restore their local reefs. “If we can do it in Hong Kong, we believe other metropolises can do it, too.”

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Rhoda Kwan

Rhoda Kwan is HKFP's Assistant Editor. She has previously written for TimeOut Hong Kong and worked at Meanjin, a literary journal. She holds a double bachelor’s degree in Law and Literature from the University of Hong Kong.