Odd Neptune balls are popping up on beaches. What are they?
If you're headed to the beach this fall, be on the lookout for Neptune balls, which capture and remove plastic from the oceans as they eventually roll back onto shore. More than 860 million pieces of plastic are estimated to be filtered out from the sea every year
While seeing plastic on beaches, or any stretch of land or waterway, is nothing out of the ordinary these days, seeing weird-looking and coloured balls on them might pique your interest.
If you come across one, or a few, they could be Neptune balls, as they're commonly called, which are actually compact, natural meadows of seagrass (Posidonia oceanica) that have washed up on land.
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At first inspection of the washed-up objects, they may not look like they contain plastics, but they do. The gently swinging plants will grab onto and combine bits of plastic pollution into balls that eventually roll onto the shoreline--as if they're spitting them out of the seafloor.
That's precisely what they do, as researchers accidentally found out, accidentally filtering and removing the plastic pollution from the ocean depths. A 2021 study in Nature highlights how that is possible.
Neptune ball. (Getty Images/robybret/2225364508-170667a)
"Our findings show that seagrass meadows promote plastic debris trapping and aggregation with natural lignocellulosic fibres, which are then ejected and escape the coastal ocean," the authors said in the study, which focused on Mallorca Island, located in the western Mediterranean Sea.
How much plastic gets trapped and filtered?
Plastics have shown up everywhere on the planet, even showing up in human blood, so it isn't surprising that they can be found on the bottom of the ocean.
Posidonia oceanica is a moderate species that often roll ashore onto beaches during the autumn--often driven to land during storms and periods of strong waves--but its leaf sheaths situated near the underground roots will get buried by sediments. It is during that ordeal that the fibres that are let go will eventually create what are called “ball-shaped agglomerates known as seaballs,” or “Neptune balls,” researchers said.
As a result, they can, and do, engulf surrounding items, including small pieces of plastic.
Posidonia oceanica spheroid on the beach. (Ezu (Martino A. Sabia)/Flickr. CC BY 2.0)
Scientists with the University of Barcelona found that plastic debris was contained in half of the loose seagrass leaf samples they collected--with 61.29 per cent of the plastic objects being small fragments. As much as 1,470 plastic items per kilogram of plant material was uncovered. The plastics were mostly made of negatively buoyant polymer filaments and fibres.
"We cannot completely know the magnitude of this plastic export to the land. However, first estimations reveal that Posidonia balls could catch up to 867 million plastics per year," said Anna Sànchez-Vidal, a researcher at the University of Barcelona and co-author of the study, in a news release.
The results of the study show how seagrasses, one of many key ecosystems that provide a buffet of benefits to our planet, can counteract marine plastic pollution, too. Seagrass meadows are abundantly found in numerous marine ecosystems, nestled in shallow, coastal regions that are 0.5 to 40 metres below the ocean’s surface.
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Thumbnail courtesy of Ezu (Martino A. Sabia)/Flickr. CC BY 2.0.
