With Neptune Balls, Ocean Hits 'Return to Sender' on Human-Made Microplastics

Each year, roughly 22 million tons of plastic pollution find their way into the world’s oceans. Now, scientists have learned that the ocean may have come up with a way to say, “No thanks.”

Dense wads of seaweed form when Posidonia oceanica sea grasses shed their leaves in autumn. Scientists call them "Neptune balls.” They are named after Neptune, the Roman god of the sea. As the seaweed grows in thick patches on the ocean floor, it acts like a net. The patches pick up smaller plastics almost like a natural filter. Ocean currents gather the shed leaves and roll them into tight balls. During that process, the tiniest pieces of plastic, known as microplastics, are caught.   

"As they move, (the Neptune balls) transport plastic intertwined within the fibers," Anna Sanchez-Vidal told the BBC. She is a lead researcher on a study of Neptune balls published in the journal Scientific Reports. 

Sanchez-Vidal estimates that Neptune balls manage to catch up to 900 million pieces of microplastic each year in the Mediterranean Sea alone. The plastics are carried to shore by the floating spheres. Many of them wash up onto beaches. There, scientists have been able to record the pollution. In some cases, they have also been able to get rid of the plastics. Yet the sea grasses that form Neptune balls are themselves under threat from pollution and climate change. Experts caution that Neptune balls are a symptom of the world’s plastic problem, not a cure.

"We say it's a way of the sea returning the trash to us that was never meant to be on the seafloor," Sanchez-Vidal told the BBC. “But it's also not a solution.” 

Reflect: What is one small change you could make in your everyday life to help protect the environment?

Photo of Posidonia oceanica spheroid on the beach from Wikimedia Commons.

Edit: Changed Nepture, Greek god to Roman god.