More than five trillion pieces of plastic weighing as much as two large cruise liners are floating in the world’s oceans, a study has shown.
The total weight of all the plastic pollution in the seas is estimated to be almost 269,000 tons.
An international team of scientists made the calculation after gathering data from 24 expeditions mounted over a period of six years between 2007 and 2013.
Towed nets were used to scoop up plastic from five subtropical ‘gyres’ − huge areas of circulating ocean currents − as well as coastal Australia, the Bay of Bengal and the Mediterranean Sea.
The oceans contained at least 5.5 trillion plastic pieces weighing 268,940 tons
Visual surveys provided information about large fragments of plastic material. Combined with the data, a computer simulation of floating debris dispersal indicated that the oceans contained at least 5.25 trillion plastic pieces weighing 268,940 tons.
The plastic ranged from tiny particles less than a millimetre wide to ‘macro’ fragments more than 20 centimetres across.
Subtropical gyres are known to gather up plastic, but the research showed that the rubbish was not confined to these ocean ‘dustbins’.
The smallest particles were distributed to remote parts of the world, including sub-polar regions, suggesting that the gyres ‘shredded’ large plastic items and ejected the pieces.
Lead researcher Marcus Eriksen, director of research at the Five Gyres Institute in Los Angeles, Los Angeles, said: “Our findings show that the garbage patches in the middle of the five subtropical gyres are not the final resting places for the world’s floating plastic trash.
“The end-game for microplastic is interactions with entire ocean ecosystems.”
Large plastics appeared to be abundant near coastlines, the scientists found. The amount of ‘microplastic’ particles on the surface of the oceans was much less than expected, suggesting that some of it was being removed.
Removal processes included degradation by sunlight, biodegradation, loss of buoyancy, entanglement with settling detritus, beaching, and ingestion by fish and other organisms.
Writing in the online journal Public Library of Science One, the scientists concluded: “This is the first study that compares all sizes of floating plastic in the world’s oceans from the largest items to small microplastics.
“Plastics of all sizes were found in all ocean regions, converging inaccumulation zones in the subtropical gyres, including southern hemisphere gyres where coastal population density is much lower than in the northern hemisphere.”