Rethinking Artificial Reef Structures via 3D Clay Printing
Corals are fundamental to marine life. Sometimes called tropical sea forests, they form some of the most diverse ecosystems on Earth. They serve as a refuge, breeding and feeding area for dozens of species at sea, and their absence can negatively affect local biodiversity. Yet the way humanity is polluted and destroyed can also encourage and encourage the creation of more lives. This is why the sinking of concrete structures for the construction of old shipwrecks or artificial reefs is often reported as providing immense potential. In Hong Kong, researchers are developing 3D printed structures using organic materials that can lead to the creation of new opportunities under the sea.
Coral reefs have existed for 485 million years and occupy approximately 284,300 km2, which is equivalent to about half the area of France. They provide shelter for at least 25% of all marine species, including fish, molluscs, insects, crustaceans, sponges, and more. Pollution commonly found in warm water, clean water, coral reefs around the world is threatened by domestic sewage, oil spills in the ocean, sedimentation and mainly by rising sea temperatures. This threat has worried environmentalists around the world. For example, in Hong Kong, Hoi Ha Wan Marine Park is home to more than three quarters of the coral species that constitute reefs in the country and is home to more than 120 species of reef-associated fish. However, the incidence of bleaching and mass mortality between 2015 and 2016, as well as a gradual decline by bioarrowing over the years, have put the local coral community at risk.
In response, a coral restoration research project was created as a collaboration between the Robotic Fabrication Lab, the University of Hong Kong Faculty of Architecture and the University of Hong Kong Swear Institute of Marine Science. The project was initiated by the Department of Agriculture, Fisheries and Conservation (AFCD), and is part of an ongoing management measure for coral restoration in Hong Kong’s Hoi Ha Wan Marine Park. Historically, artificial rocks have been made of polluting materials such as plastic, concrete or metal. Now, however, there are alternatives to using environmentally friendly materials such as ceramic and terracotta. HKU’s project team uses 3D printing technology to engineer structures that can be adapted to specific locations with various environmental challenges (such as sedimentation), thus increasing the success of ecological restoration. The team of marine biologists and architects have thus developed a series of 3D-printed terracotta reef structures, which provide structurally complex substrates in a degraded area, to aid in coral restoration.
3D printed reef tiles are designed to prevent sediment formation, which is one of the major threats to coral reefs. A tailored algorithm was used to print integrated biomimicry patterns with blanks to secure coral fractions. Production of 128 pieces of reef tiles with a diameter of 600 mm, covering a total of about 40 sqm, was started in July of 2020. They were printed with generic terracotta clay through a robotic 3D clay printing method and then fired at 1125 degrees. Celsius. The design was uniquely inspired by the pattern of corals and integrated many demonstrative aspects addressing specific situations in Hong Kong waters. 3D printed reef tiles are deployed in July 2020 at three select sites within the park including Coral Beach, Moon Island and in a shelter bay near the WWF Marine Life Education Center.
The purpose of this pilot study is to investigate restoration success using mono-, mix-, and polyculture of three coral species, Acropora, Platygra, And Pavona. The three selected species incorporate various strategies, representing the historical, current and future prime candidates in the park – Acropora, Commonly known as staghorn corals, grow rapidly, making them species competing for space; Platygyra, Known as brain corals, is conducive to thermal stress, yet suffers from bioerosion; And Pavona, Leaf coral, as a unique plate-like growth, is favorable to sedimentation. The project team collected corals of opportunity, which are coral fragmented that are unlikely to survive without human intervention, and gave these coral fragments a second chance to flourish. The piece of coral has been removed in July 2020, and the experiment will be monitored for the coming year.
Researchers hope that this new method of making artificial reef tiles will help restore corals and preserve biodiversity, as a significant contribution to ongoing global efforts to conserve coral declining coral reef systems.