How much plastic debris is floating in the world’s oceans? Maybe a lot less than was anticipated.
A new study has found that plastic pollution in the open ocean is widespread but less than predicted due to an “unknown sink for small plastic particles”.
Published in the U.S. journal Proceedings of the National Academy of Sciences (PNAS), the study – coauthored by scientists at the University of Western Australia’s Oceans Institute (UWA) and universities in Saudi Arabia and Spain – found that plastic waste debris in the ocean is widespread, but that an “unknown mechanism” is removing small plastic fragments at a higher rate than larger fragments.
“A conservative first-order estimate of the floating plastic released into the open ocean from the 1970s (106 tons) is 100-fold larger than our estimate of the current load of plastic stored in the ocean,” the report said. “Our study reports an important gap in the size distribution of floating plastic debris as well as a global surface load of plastic well below that expected from production and input rates.”
The study authors collected 3,070 ocean surface samples at 141 sites around the world and found that 88 per cent of the samples contained plastic debris of varying sizes with highest plastics concentrations in the five so-called subtropical ocean gyres (a gyre is a large system of rotating ocean currents, particularly those involved with large wind movements).
Particle size analysis revealed a low concentration of plastic fragments smaller than one millimetre in diameter in the samples. In addition, the estimated total ocean plastic content, on the order of tens of thousands of tons, was much less than previous estimates predicted.
Further research is needed to determine which ocean life or systems are responsible for the disappearance of small plastic fragments and how they may be affected by exposure to or ingestion of plastic waste, the report said.