Amsterdam, 12 September 2019 – A new form of the plastic soup has been discovered on the coast of the Atlantic island of Madeira. Plastic crusts are growing on the rocks in the intertidal zone. These crusts are blue or white in color. In contrast to other washed-up plastic, that in principle can be removed during cleanups, this plastic cannot be dislodged. The phenomenon is called plasticrust (plastic crust). Read here the article in Science of the Total Environment.

Volcanic rock

The black volcanic rocks of Madeira become very hot under the sun, and it appears that plastic particles left behind at low tide have melted and stuck. These particles become attached to the substrate and to each other. These are polyethylene (PE) crusts. Polyethylene is the most common type of plastic and is often used in packaging. These plastic deposits can now be found on ten percent of the rocks that are not immersed at low tide. In 2016, the phenomenon was first noticed by Ignacio Gestoso, a researcher at the Marine and Environment Sciences Center (MARE). Back then it was observed at only one location. Over the past three years, Gestoso has seen a significant increase in the amount of plasticrust. This is an indicator of the increasing pollution in the sea around Madeira.

Impact on marine life?

The periwinkle (Littorina littorea) lives off algae which grows on the rocks. These sea snails are found on both the rocks and the plasticrusts. Researchers therefore suspect that the periwinkle is also eating the plastic. Perhaps this also applies to other organisms, in which case it is a new way that plastic particles can enter the marine food chain. And there is another problem: expansion of the plastic crusts reduces the area of natural algal crusts, which provide food to marine organisms.

Plastiglomerate and pyroplastics

Plasticrust is a kind of plastic sediment and apparently the conditions are favorable for it in Madeira. It is reminiscent of a geological process. However, plasticrust is not comparable with plastiglomerate (molten plastic that has been mixed with other material such as coral and stones) or pyroplastics (molten plastic that has been shaped during a long period at sea). Those are caused by people burning plastic, not by melting plastic washed up by the sea.

Photo: Ignacio Gestoso

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