Rethinking artificial barrier structures through clay 3D printing
Corals are critical to marine life. Sometimes called tropical marine forests, they form some of the most diverse ecosystems on Earth. They serve as a refuge, breeding and feeding ground for dozens of species in the sea, and their absence can negatively impact local biodiversity to an enormous extent. However, just as humanity pollutes and destroys, it can also remedy and encourage the creation of more life. This is why wrecks of old ships or the sinking of concrete structures to create artificial reefs are often reported as immense potentials. In Hong Kong, researchers have developed 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 about 284,300 km2, which is about half the area of France. They provide shelter for at least 25% of all marine species, including fish, mollusks, worms, crustaceans, sponges and more. Generally found in warmer and clearer waters, coral reefs around the world are threatened by pollution from domestic sewage, oil spills into the sea, sedimentation, and, primarily, rising ocean temperatures. This threat has worried environmentalists around the world. In Hong Kong, for example, the Hoi Ha Wan Marine Park is home to more than three-quarters of the coral species that make up the country’s coral reefs and is home to more than 120 reef-associated fish species. However, the gradual deterioration due to bioerosion over the years, coupled with bleaching events and mass mortality between the years 2015 and 2016, put the local coral community at risk.
In response, a coral restoration research project was created in collaboration between the Robotic Fabrication Lab, the University of Hong Kong’s Faculty of Architecture and the University of Hong Kong’s Swire Institute of Marine Science. The project was commissioned by the Department of Agriculture, Fisheries and Conservation (AFCD) and is part of an ongoing management measure to restore coral in Hong Kong’s Hoi Ha Wan Marine Park. Historically, man-made barriers have been made with polluting materials such as plastic, concrete or metal. Now, however, there are options for using environmentally friendly materials, such as ceramic and terracotta. HKU’s project team uses 3D printing technology to design structures that can be customized for specific locations with different environmental challenges (e.g. sedimentation), thereby enhancing the success of the ecological restoration. The team of marine biologists and architects then developed a series of 3D printed terracotta coral reef structures to assist in the restoration of the corals, providing structurally complex substrates in a degraded area.
The 3D printed reef tiles are designed to prevent sedimentation buildup, which is a major threat to coral reefs. A custom algorithm was used to print the integrated biomimicry models with spaces for the protection of the coral fragments. Production of the 128 pieces of coral reef tiles with a diameter of 600 mm, covering approximately 40 square meters in total, was completed in early July 2020. They were printed using a robotic 3D printing method with terra cotta clay. generic and then cooked at 1125 degrees. Centigrade. The design was inspired by typical coral patterns and integrated several performative aspects that address specific conditions in Hong Kong waters. The 3D printed coral reef tiles were installed in July 2020 at three select sites within the park which include Coral Beach, Moon Island, and in a sheltered bay near the WWF Marine Life Education Center.
This pilot study aims to investigate the successful restoration using mono-, mix- and polyculture of three coral species, namely Acropora, Platygyra, is Pavona. The three selected species comprise different strategies, representing historical, current and future dominant candidates in the park – Acropora, commonly known as staghorn corals, are fast growing, making them a competitive species for space; Platygyra, known as brain corals, adapt to heat stress but suffer from bioerosion; is Pavona, the leaf coral, with a form of growth similar to a plate, is adaptable to sedimentation. The project team collected opportunity corals, which are detached coral fragments that are unlikely to survive without human intervention, and gave these coral fragments a second chance to thrive. The coral fragments were transplanted in July 2020 and the experiment will be monitored for next year.
The researchers hope that this new method of creating artificial reef shingles will help restore corals and conserve biodiversity more effectively, becoming a vital contributor to ongoing global efforts to save degraded reef systems in metropolises.