Seagrass’s Neptune Balls Sift Millions of Plastic Particles in Water, Study Finds | Plastics

Seagrass beds in coastal areas appear to trap plastic pollution in natural bundles of fibers called “neptune balls,” researchers have found.

Without the help of humans, swaying plants – rooted in the shallow seabed – can collect nearly 900 million plastic items in the Mediterranean alone each year, according to a study published in the journal Scientific Reports.

“We show that plastic debris from the seabed can be trapped in seagrass remains, eventually leaving the marine environment by stranding,” lead author Anna Sanchez-Vidal, marine biologist at the AFP, told AFP. University of Barcelona.

This cleaning “represents a continuous purge of plastic debris out of the sea,” she added.

The study adds to the long list of services provided by seagrass beds – for ocean ecosystems and humans who live near water’s edge. They play a vital role in improving water quality, absorb CO2 and exude oxygen, and are a natural nursery and refuge for hundreds of species of fish. They are also at the base of coastal food webs.

By anchoring in shallow water, they help prevent beach erosion and cushion the impact of destructive storm surges.

There are 70 species of sea grasses, grouped into several families of flowering plants that – originally on land – recolonized the ocean 80 to 100 meters ago.

Growing from the Arctic to the tropics, most species have long grass-like leaves that can form vast underwater prairies.

It is not known whether collecting the plastic damages the seagrass beds themselves.

To better understand the plastic clustering capacities of seagrass beds, Sanchez-Vidal and his team studied a species found only in the Mediterranean Sea, Posidonia oceanica.

In 2018 and 2019, they counted the number of plastic particles found in sea balls that had washed up on four beaches in Mallorca, Spain, which has large sea meadows offshore.

There was plastic debris in half of the loose seagrass leaf samples, up to 600 pieces per kilogram of leaves.

Only 17% of the tighter bundled seagrass fiber known as Neptune Balls contained plastic, but at a much higher density – nearly 1,500 pieces per kilogram of seaballs.

Using estimates of the production of seagrass fibers in the Mediterranean, the researchers established an estimate of the amount of plastic that could be filtered throughout the basin.

Oval orbs – shaped like a rugby ball – form from the base of leaves that have been torn apart by the action of ocean currents but remain attached to stems, called rhizomes.

As they are slowly buried by sedimentation, the damaged leaf sheaths form stiff fibers that intertwine into a ball, collecting plastic in the process.

“We don’t know where they are traveling,” Sanchez-Vidal said. “We only know that some of them are stranded during storms.”

In 2018, WWF estimated that in just a few weeks during the Mediterranean holiday season, increasing marine plastic pollution contributed to around 150 million tonnes of plastic in the ocean.