Clay Culture: Tiling Coral Reef Lisa McDonald

Appears in the April 2021 issue of Ceramics Monthly.

Artificial 3D-printed ceramic reef tiles are specially designed by architects and marine scientists to aid in coral restoration by providing a structurally complex foundation for coral attachment.

My family typically tries to coordinate vacations so that we can all travel together, but during a busy college finals season in 2015, I watched with jealousy when my dad traveled to Australia for a week to take a scuba-diving trip to the Great Barrier Reef off the east coast of mainland Australia, near Queensland.

My dad has wanted to explore the Great Barrier Reef for years—he was an avid diver during his college years—but recent ecological events gave him the urgency to finally schedule the trip. Specifically, the 2014–17 global-scale coral bleaching event.

During this unprecedented period of successive years of record-breaking temperatures, more than 75% of global reefs experienced mass heat stress and nearly 30% reached mortality levels, according to the National Oceanic and Atmospheric Administration (NOAA) for Coastal Management. Early in 2020, scientists reported another mass bleaching event, this one larger in scale and second only to the year 2016 in intensity.

The mass bleaching worries scientists because once corals die, reefs rarely come back. And without coral reefs, many marine animals will lose their homes, coastal communities will lose protection from flooding, and people who rely on reef fisheries for food and income will go hungry, among other adverse effects. So, restoring coral reefs damaged by bleaching as well as ocean acidification and pollution is an important and urgent task for marine researchers.

Among the numerous approaches to restoration, one method called structural restoration involves introducing artificial structures into areas where the reef was lost due to disturbances such as blast fishing, boat grounding, dredging, and landslides. In such circumstances, the seafloor is reduced to rubble or sand, and coral cannot attach to these loose surfaces. The artificial structures provide a solid surface to which the coral can attach.

To create these artificial structures, a team of marine scientists and architects at the University of Hong Kong recently explored using 3D printing to fabricate structurally complex clay tiles (2–4). They initially considered using concrete or metal, but they decided on terra-cotta clay because it is more environmentally friendly.

In July of 2020, the researchers seeded the almost 2-foot-wide hexagonal tiles with three species of coral fragments (Acropora, Platygyra, and Pavona) (1) and then planted 128 tiles (5) at three different sites in Hong Kong’s Hoi Ha Wan Marine Park. They chose this marine park because, in 2018, Typhoon Mangkhut destroyed nearly 80% of the coral reefs in the Hoi Ha Wan bay, which is home to 60 species of coral as well as 120 fish species.

After two months, the scientists observed that 100% of the coral on the tiles still thrived (6, 7). They plan to continue monitoring the site for the next one and a half years.

Watch the following video to learn more about the terra-cotta reef tiles project at www.youtube.com/watch?v=G7VR08z99iU.

the author Lisa McDonald is the associate managing editor and science writer at The American Ceramic Society. Prior to this position, McDonald worked at the American Institute of Physics: FYI and the ATLAS Experiment at CERN. She has a master’s degree in science communication and specializes in communicating science to nonspecialist audiences.