The quantity of plastic present in the oceans re-evaluated sharply on the rise

The emblematic images of Sausage turtles in tarp debris or birds nesting among plastic bottle caps on a beach are only part of the marine pollution problem. Because in addition to the millions of tonnes of packaging, remains of fishing gear and other aquatic macro-waste, there are five times more microplastic particles floating in the world ocean than what the scientific community estimated until 2015. The study published Thursday, September 9 in the journal Microplastics and Nanoplastics, of the group Nature, does not claim that the quantities, admittedly gigantic, of microplastics present in the water have exploded in a few years, but explains that previous work had greatly underestimated the level of pollution.

According to the international team led by Atsuhiko Isobe of the Center for Oceanic and Atmospheric Research at Kyushu University (Japan), there are 24.4 trillion (billion billion) of these particles with a size of between 1 and 5 millimeters suspended in the oceans, not 5.5 trillion, as initially estimated; which would represent between 82,000 and 578,000 tonnes. The analyzes detected on average between 113,000 and 5.3 million pieces of microplastics per square kilometer, or a weight of 130 grams to 2.67 kilos.

Generalized contamination

The authors analyzed, calibrated and synthesized the raw data drawn from 8,218 samples, which were collected around the globe and which are intended to feed a public database. However, they point out that in their mesh of the oceans, elements from the western Indian Ocean and the South China Sea are missing, while “South, Southeast Asia and China generate around 68% of all poorly managed plastic waste in the world”.

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From coastal waters to deep sea abysses, contamination is widespread – even if knowledge of these deep waters is limited by the difficulty of carrying out research there. Citing recent studies, the publication notes in particular that microorganisms which develop on the surface of submerged elements (ships, dikes, etc.), incorporated into marine aggregates and faeces, “Allow microplastics lighter than sea water to settle in the abyssal ocean”. The samples taken for the study mainly come from water close to the surface.

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