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  • Alexandra Jacobo

There’s a new plastic on the rock

Updated: Jan 4

We know it’s taking over our oceans and beaches — an estimated seven million tonnes of plastic ends up in our oceans every year, and growing. But now, like everything else in nature, some of it is evolving.

Researchers have discovered a new, maybe even more permanent, form of plastic pollution, which they’ve dubbed ‘plasticrust’. Bits of plastic are being incorporated right into the rocky shoreline of the Portuguese island of Madeira.

In 2016, marine ecologist Ignacio Gestoso of the Marine and Environmental Research Centre on Madeira, noticed that a light blue film was forming as a crust on the island's volcanic shoreline much as old chewing gum grafts onto a footpath. At the time, it was assumed it was a one-off.

However, when researchers returned the following year, the crusts were still there. A year later, they returned to find not only was the ‘plasticrust‘ still there but it had grown, spreading out over a larger area and in multiple colours. After three years, the plasticrust has grown from a single area to cover almost 10 percent of the rocks’ surfaces.

Samples taken reveal the plasticrust to be made of polyethylene, a common plastic used in single-use packaging and food containers.

The research team published its findings in the June 2019 edition of Science of the Total Environment. “[The crusts] likely originated from the crash of large pieces of plastic against the rocky shore, resulting in plastic crusting the rock in a similar way algae or lichens do,” says Gestoso. It is not yet known how the plasticrust will affect the ecosystem on the island. Many intertidal animals stick to these shoreline rocks and feed from the algae that usually grows on them. After observing the winkle sea snail on the plasticrust surfaces, Gestoso’s team found the snails didn’t avoid the plasticrust surfaces, meaning they could be eating algae that settles on top of the plastic pollution and therefore may be ingesting some of the plastic in the process.

While this plasticrust appears to be a new form of plastic pollution, back in 2013, researchers found a merger of plastic and rock in Hawaii, which they called ‘plastiglomerate’. It was the result of campers burning plastic waste in campfires, which ended up bonding with sand and pebbles.

Plastics disintegrate when exposed to the sun, breaking down to millions of smaller pieces, known as microplastics. Those pieces can be so small that bits of plastic from a one litre plastic beverage bottle could end up on every stretch of beach across the planet.


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