Super-typhoon ‘Mangkhut’ devastated Hong Kong in 2018, flooding the city, uprooting trees and damaging buildings. The coral reef of Hoi Ha Wan Marine Park also fell victim to the typhoon. It was home to more than 60 species of coral and 120 species of coral fish.
Architects from the Robotic Fabrication Lab and marine scientists at the University of Hong Kong worked together to speed up regeneration by creating artificial ‘kick-starter’ reefs using 3D printing.
Growth rates for hard coral range between 0.3 to 2 centimetres per year and can take up to 10,000 years to form: the Great Barrier reef is earth’s largest living structure and its last formation since the Ice Age dates back 8,000 years.
Coral Reefs are “Rainforests of the Seas”
Coral reefs occupy only 0.1 per cent of the ocean, yet they sustain life by supporting one of the most diverse ecosystems on our planet.
Corals are a host for algae, and this symbiotic relationship provides food and shelter for 25 per cent of all marine life. The reefs also serve as nurseries for juvenile fish. The gravity of the destruction of coral reefs cannot be underestimated. Scientists are still discovering new species every year. The biodiversity is key to sourcing new compounds for medicines. It supports our fishing industries as well as tourism. Coral reef structures also protect our coastline from 97 per cent of the energy from waves and storms.
Marine scientists have been fighting against its decline for decades. Higher water temperatures as a result of climate change, overfishing and destructive fishing practices, and pollution, have devastated our reefs faster than they can regenerate.
Heat-stress due to rising temperatures has accelerated coral bleaching. Severe mass bleaching which tended to occur every 27 years has accelerated to every 6 years since the 1980s. Between 2014 and 2017, 75 per cent of the Earth’s tropical reefs were affected, 30 per cent were killed.
How do 3D-Printed Reef Tiles Work?
Artificial terracotta ‘reef tiles’ replicate the intricate patterns of corals and acts as a support base for coral larvae to grow on. It is much harder to kick-start growth of new coral when the seabed has been flattened and there is nothing for free-swimming coral fragments to anchor themselves to.
More traditional methods of restoring coral reefs have included farming coral either in tanks or in the ocean and transplanting them.
Three sites spanning a total of 40 square meters within the marine park have been covered with 128 fabricated tiles. The tiles have also been seeded with three native coral species with different growth forms to recreate a diverse habitat. Perforations in the tiles allow coral fragments to be seeded. Hong Kong’s waters have a lot of sedimentation, the holes also ensure that sediment doesn’t deposit on the surface and suffocate the corals.
The clay hexagon-shaped tiles are biodegradable and will naturally degrade as coral grows over it. Once it settles and matures, they hope coral colonies will expand naturally by spawning or division of polyps. Research from the University of Delaware demonstrated that 3D-printed coral models do not affect coral larvae settling on it or fish making it their habitat.
Researchers will monitor their growth and success over the next one and a half years. They plan to adapt and expand their efforts for coral reef restoration to other areas in the region.