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Japanese universities are seeking to restore coral reefs and marine ecosystems after inheriting artificial coral structures that Saudi Arabia made and showcased at this year’s World Exposition in Osaka.

The coral skeletons, donated to the University of the Ryukyus in Okinawa and Kansai University in Osaka Prefecture, are made of calcium carbonate, a material on which corals are believed to grow more easily when compared with other artificial alternatives such as concrete or metal.

The skeletal structures were created using 3-D printers, with one piece produced per day during the expo period and displayed across an entire wall in the Saudi Arabian pavilion’s area themed around sustainable marine environments.

Coral reefs serve as habitats for much marine life, but over 40% of the world’s 892 coral species face the risk of extinction, according to the International Union for Conservation of Nature.

The University of the Ryukyus, which received about 150 of the artificial coral skeletons, will place them in waters off the eastern coast of Okinawa’s main island and then examine their impact on the ecosystem.

“We wish to see if these 3-D printed corals will serve as homes for various organisms…we need to see how they act and interact in nature with the coral reef ecosystem,” said James Davis Reimer, a marine biology professor at the university. He noted that many coral reefs in Okinawa have already died.