Nature’s Seagrass Mystery
After storms, Mediterranean beaches often reveal curious brown spheres called “Neptune balls.” These fibrous bundles don’t come from factories but from Posidonia oceanica, a seagrass that grows in dense underwater meadows. As the plant sheds old leaves, their tough sheaths break away and tangle together. Waves then roll these fibers into compact balls that eventually wash ashore.
How They Trap Plastic
Scientists recently discovered that these Neptune balls carry fragments of plastic. Ocean currents stir up the seafloor and push microplastics into seagrass meadows. The fibrous sheaths grab these particles and lock them in. As the fibers clump together, they trap even more debris, turning Neptune balls into natural sweepers that transport plastic from the ocean to the shore.
Measuring the Plastic Load
Researchers in the Balearic Islands collected samples to measure the plastic content. They found that loose seagrass leaves already held hundreds of fragments per kilogram. Neptune balls, however, packed a much heavier load. While fewer of them contained plastic, those that did carried up to 1,500 pieces per kilogram. Scientists estimate that seagrass meadows in the Mediterranean may remove nearly a billion plastic particles from the sea every year through this process.
An Unlikely Ally Against Pollution
Seagrass meadows do more than nurture marine life and capture carbon—they actively help fight pollution. By sweeping plastics from the sea and exporting them onto beaches, they play an unexpected but crucial role in cleaning the oceans. Yet these meadows face growing threats from climate change and coastal development. Protecting them will not only preserve biodiversity but also strengthen one of nature’s most surprising defenses against marine plastic.
