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Marine Microbes Munch on Plastic Waste

Tiny plastic particles floating in the sea are providing a home to microscopic marine creatures, according to research published in PLOS One. The sand-sized plastics come from the breakdown of discarded plastic items such as single-use packaging and fishing gear.

The research team behind the discovery believes that some of the plastic inhabitants may decrease plastic pollution level at the sea surface, where major environmental impacts occur. Study co-author Dr Jeremy Shaw of The University of Western Australia (UWA) says that large numbers of silica-forming algae weighed down their plastic host, potentially causing tiny pieces to sink to the bottom of the ocean.

The research team took more than 1000 electron microscope images of ocean plastics, and were also able to see colonies of microbes that seem to be “eating plastics”. PhD candidate Julia Reisser says that “the ‘plastic-eating’ microbes could provide solutions for better waste disposal practices on land”.

However, she notes that “epiplastic” organisms could also make ocean plastics more attractive as food for animals, leading to un­anticipated ingestion of plastic. Furthermore, species that live on ocean plastic could disperse across oceans, potentially invading new habitats and impacting local ecosystems.

In separate UWA research published in the Proceedings of the National Academy of Sciences, Prof Carlos Duarte and international collaborators found that plastic pollution in the open ocean is widespread but less than predicted, with elevated levels in each of the five subtropical gyres of the ocean. A gyre is a large system of rotating ocean currents.

The authors found that 88% of the 3070 ocean surface samples collected at 141 sites around the world contained plastic debris of varying sizes, with a low concentration of plastic fragments smaller than 1 mm in diameter. The total amount of plastic in the oceans, in the order of tens of thousands of tonnes, was less than previous estimates had predicted, suggesting that some mechanism is removing small plastic fragments at a higher rate than larger fragments.

The authors noted that the concentration of plastic debris in ocean samples rose in line with mass production of plastics in the middle of the 20th century, but levelled off in the 1980s.