Engineers say artificial reefs could filter microplastics from the sea

WHAT if we could build artificial coral reefs to filter microplastics from the sea? That’s a possibility put forward by engineers in Canada who have been looking at how living reefs are becoming clogged with plastic pollution.

It’s no secret that coral reefs are struggling to cope with the stresses unleashed by climate change and pollution. Increases in water temperature have halved shallow water corals of Australia’s Great Barrier Reef. Corals are also sensitive to CO2 concentrations – increases make the ocean more acidic which hinders corals from the building skeletons that form the reefs. In a calamitous twist, this puts us at more risk as healthy reefs break waves and reduce flooding.

Add in the harmful effects suffered by corals trying to eat tiny fragments of plastic and its apparent they are struggling at every turn. Corals are estimated to provide habitat for 25% of all marine life and an estimated US$172bn a year in economic value through tourism, food production, and coastal infrastructure protection.

The engineers at Canada’s University of Waterloo hope their research can help identify ways to protect corals and develop new strategies for tackling plastic pollution. The team conducted tests on synthetic coral and real coral in their lab to better understand how microplastics stick to their fleshy parts.

Waterloo researcher Boxin Zhao, a professor in the university’s chemical engineering department, said: “We are the first group to quantify the mechanism of microplastic trapping on coral reefs via its mucus layer by directly measuring adhesion between mucus and microplastics. This discovery is critical because it helps us understand how microplastics are trapped in coral ecosystems, which is vital for developing effective removal strategies.”

The team says its next step will be to use their findings to develop cleanup technologies to capture microplastics and protect marine life, noting any future removal techniques must ensure microplastics removed from reefs don’t just float back into ocean water.

Study co-author Sushanta Mitra added: “By understanding the forces involved in microplastic adhesion, we can design solutions that not only prevent further harm but also mitigate further microplastic pollution in coral reefs.”

The team says that one of the most promising possibilities involves constructing artificial coral reefs inspired by living reefs that can collect plastic pollutants to help ocean cleanup efforts.

Zhao said: “I envision that artificial coral reefs will have mucus-like surfaces capable of trapping microplastics upon contact. These surfaces will exhibit higher adhesion forces to microplastics compared to seawater and other particles, allowing for selective separation. Achieving this is challenging, but it could be possible in the future.”

The study is published in the journal ACS ES&T Water.