How oyster shells can reverse man-made damage in the ocean

By Alyssa Leong

During Easter break, attracted by the title of the sharing, “Oyster Hotel”, I went to see a presentation on the subject of oyster shells and biodiversity. After a long walk through the rain we finally arrived at the building, which was purple, now dark against the white fog over the sea. Once we entered, there was a sense of relief at reaching the warm and dry place, giving me a hopeful feeling.

Welcoming me on one side of the room was a fish tank full of water, with a row of oysters connected by a rope within. The oyster shells were brown and moldy-looking and the water was mildly discolored. It was hard to understand how they could benefit the environment. But the spokesperson there revealed that the minuscule semi-transparent tentacles attached to the shells, waving in the water, belonged to barnacles. He also pointed out some spirally worms on the underside of an oyster shell. In fact, the shells contained countless creatures.

After a few minutes of waiting the talk started. Professor Kenneth Leung, Chair Professor of Environmental Toxicology and Chemistry and director of the State Key Laboratory of Marine Pollution at City University of Hong Kong, was the speaker. He started describing his project to increase the biodiversity of coastlines in Hong Kong. The current man-made coastlines come in 2 variations, the vertical seawall, and the slope made of piled rocks. However, neither of these can compare in biodiversity to natural shores, the reason being that they aren’t complex enough. They are just repetitive environments, without any crevices that water could be stored in and holes for animals to hide within. A real natural shore would have little pools, cracks, dry rocks, and such. So he set out to increase the complexity. One way was the oyster shells. Though the empty oyster shells were viewed as trash, they actually produced a complex environment for the small animals. Some strings of oyster shells were left in a metal box near the shore, underwater, and when a diver went to check on them some time later, he found that there were many organisms such as barnacles and worms on the shells, and there were many fish gathered around. Oysters themselves are filter feeders, so they are also capable of purifying water, providing another important environmental function.

Professor Leung explains the various designs of eco-tiles, simulating a natural environment to create biodiversity.

Another experiment was attaching some tiles to shores. Some of the tiles were completely smooth, while some of them had crevices and holes 25 mm deep and 50 mm deep. The end result was that the tiles with the deepest cracks contained the most sea life, showing the importance of these holes and hiding places for marine life.

The program was interesting in that they incorporated the community in helping to increase the shoreline biodiversity. There were many workshops held with schools and organizations where participants learned about the oyster shells, and took part in drilling holes and connecting them using strings. So through workshops, people learned more about oyster shells and ocean protection, while they were also able to put this into action and contribute to helping the program more directly in a satisfying way, which is a rare opportunity. And the oyster shells strung together by the participants in turn benefitted the program.

Additionally, they collaborated with City University of Hong Kong to design better tiles for the shore that could increase biodiversity. This required knowledge of ecology, but also engineering. They eventually resulted in the Eco-Tile, a tile equipped with grooves and cracks which provided shelter from predators and a cool environment for animals to live in. It was a success. After being left for a year on a manmade vertical seawall, the Eco-Tile had twice as many species as the wall did. Additionally they created a startup called afterNature that sells panels which contain many holes and crevices of different sizes to store water so animals would not get dehydrated. They are also curved so that some part of them will always be in the shade, no matter where the sun is. It is an interesting imitation of a natural environment where animals could thrive. I thought this innovative design was very detailed and well-developed.

This project shows that helping to restore biodiversity is a collective action which requires input from not just experts, but also communities and governments. Also the project was worth something for the participants; people who participated in the workshops got to learn about ocean protection and this benefits the marine environment of the future. Humans can do more than reduce the damage to the environment through passive actions like lowering the amount of waste. We can also reverse the damage.