We keep finding marine plastic

There’s mixed news in our fight against plastics that cause chaos in marine environments. We’re finding new ways to find it, but we’re still finding much too much of it.

Two new studies from either side of the world make the point.

In the UK, researchers from the Plymouth Marine Laboratory have developed a way to detect floating macroplastics (larger than five millimetres) using data from the European Space Agency Sentinel-2 satellites.

In a paper in the journal Scientific Reports, they report being able to distinguish plastics from other materials with 86% accuracy across four locations.

Lauren Biermann and colleagues from Plymouth and the University of the Aegean, Greece, identified patches of debris by their spectral signatures – the wavelengths of visible and infrared light they absorbed and reflected – then trained a machine-learning algorithm to classify the individual materials that made up these patches according to the specific spectral signatures of different plastic and natural materials.

These signatures were obtained from satellite data on plastic litter washed up in the Durban Harbour in South Africa and floating plastic deployed by the authors off the coast of Mytilene, Greece. They also used earlier data on natural materials likely to be found together with marine plastic, such as seaweed, woody debris, foam and volcanic rock.

They report testing their method successfully using data from coastal waters in Accra (Ghana), the San Juan islands (US), Da Nang (Vietnam) and east Scotland. They achieved 100% accuracy off San Juan.

In Australia, meanwhile, a research team led by the Institute for Marine and Antarctic Studies (IMAS) believes it has recorded microplastic pollution in Antarctic sea ice for the first time.

Writing in the Marine Pollution Bulletin, it says analysis of an ice core collected in East Antarctica in 2009 found 96 microplastic particles from 14 different types of polymer.

Lead author Anna Kelly says plastic pollution has been recorded in Antarctic surface waters and sediments, as well as in Arctic sea ice, but this is thought to be the first time it has been found in Antarctic sea ice.

“The ice core we analysed was from coastal land-fast sea ice and averaged almost 12 particles of microplastic per litre,” she says.

“While this concentration is lower than that found in some Arctic sea ice samples, the 14 different polymer types we identified is only slightly less than the 17 found in Arctic studies.

“The microplastic polymers in our ice core were larger than those in the Arctic, which may indicate local pollution sources because the plastic has less time to break down into smaller fibres than if transported long distances on ocean currents.”

Kelly says the findings highlight the potential for sea ice to be a significant reservoir for microplastic pollution in the Southern Ocean.

“It is worth noting that plastic contamination of West Antarctic sea ice may be even greater than in our ice core from the East, as the Antarctic Peninsula hosts the bulk of the continent’s tourism, research stations and marine traffic,” she adds.

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