Marine scientists have broken new ground in the pursuit of a better understanding of how microplastics accumulate in coral reefs, providing a key stepping stone towards increased and more efficient ways to protect vulnerable ecosystems from plastic pollution.

Researchers from the University of Waterloo’s Faculty of Engineering used nanotechnology to determine that it is the mucus naturally secreted by coral reefs – a substance that bears strong adhesive characteristics – that traps microplastics floating in the ocean.

“This discovery is critical because it helps us understand how microplastics attach to coral ecosystems, which is vital for developing effective removal strategies,” said Dr Boxin Zhao, a professor in the Department of Chemical Engineering and a member of the Waterloo Institute for Nanotechnology.

Coral reefs are important, diverse ecosystems that provide food, shelter, breeding grounds, and nurseries for millions of species – about a quarter of all marine life.They also play a crucial role in filtering water, creating oxygen, and protecting shorelines from the destructive impact of coastal flooding and storms.

It’s no secret that coral reef ecosystems are also facing mounting pressures from climate change. Recent months have seen them endure what is now recognised as the fourth and most devastating mass coral bleaching event. Most recently, officials in Western Australia linked a mass coral bleaching event across the Kimberley to an escalating marine heatwave that left more than 30,000 fish dead in its wake.

In addition to the devastation brought about by a changing climate and a warming ocean, the world’s coral reefs are now facing another adversary in the microplastics now routinely building up on their branches. Coral now becomes the latest in a long line of marine life directly impacted by ocean plastic pollution.

Looking to bring a new perspective in material science to the issue of microplastics in the marine environment, researchers used nanotechnology to examine the interface between coral reefs and microplastics. 

In a unique experiment, they created a simulated environment in the lab to mimic conditions in an actual coral reef before running mechanical adhesion tests on both a real reef and the synthetic reef to measure contact forces and identify mucus as the cause of microplastic adhesion.

The next step for the research group then, is to use this new insight to develop pioneering new cleanup technologies to capture microplastics and protect marine life. Removal strategies must ensure microplastics from reefs don’t just float back into ocean water.

Researchers at the University of Waterloo have suggested that one of the ‘most promising possibilities’ is in the construction of artificial coral reefs which can “divert and collect” plastic pollutants to improve ocean remediation efforts.

“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,” said Dr Sushanta Mitra, executive director of the Waterloo Institute for Nanotechnology.

The study, called Unlocking Passive Collection of Microplastics in Coral Reefs by Adhesion Measurements was published in the scientific journal ACS ES&T Water.

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