Modelling the global distribution and risk of small floating plastic debris

Erik van Sebille1, Chris Wilcox2, Laurent Lebreton3, Nikolai A Maximenko4, Peter Sherman5, Britta Denise Hardesty2, Jan A van Franeker6, Marcus Eriksen7, David Siegel8, Francois Galgani9 and Kara L Lavender Law10, (1)Imperial College London, Grantham Institute, London, SW7, United Kingdom, (2)CSIRO, Oceans and Atmosphere Business Unit, Hobart, Australia, (3)The Ocean Cleanup, Raglan, New Zealand, (4)University of Hawaii at Manoa, Honolulu, HI, United States, (5)Imperial College London, Grantham Institute, London, United Kingdom, (6)Wageningen-UR, IMARES, Den Burg, Netherlands, (7)Five Gyres Institute, Los Angeles, CA, United States, (8)University of California Santa Barbara, Earth Research Institute and Department of Geography, Santa Barbara, CA, United States, (9)IFREMER, Bastia, France, (10)Sea Education Association, Woods Hole, MA, United States
Microplastic debris floating at the ocean surface can harm marine life. Understanding the severity of this harm requires knowledge of plastic abundance and distributions. Dozens of expeditions measuring microplastics have been carried out since the 1970s, but they have primarily focused on the North Pacific and North Atlantic accumulation zones, with much sparser coverage elsewhere. Here, we use the largest dataset of microplastic measurements collated to date to assess the confidence we can have in global estimates of microplastic abundance and mass. We use a rigorous statistical framework to standardize a global dataset of plastic marine debris measured using surface-trawling plankton nets and coupled this with three different ocean circulation models to spatially interpolate the observations.

Our estimates show that the accumulated number of microplastic particles in 2014 ranges from 15 to 51 trillion particles, weighing between 93 and 236 thousand metric tons, which is only approximately 1% of global plastic waste available to enter the ocean in the year 2010. These estimates are larger than previous global estimates, but vary widely because the scarcity of data in most of the world ocean, differences in model formulations, and fundamental knowledge gaps in the sources, transformations and fates of microplastics in the ocean.

We then use this global distribution of small floating plastic debris to (i) map out where in the ocean the risk to marine life (seabirds, plankton growth) is greatest and to (ii) show that mitigation of the plastic problem can most aptly be done near coastlines, particularly in Asia, rather than in the centres of the gyres.