Oceans of trash… Literally

We are littering the planet. We already knew that, but now a new survey published this week in the journal PLOS ONE confirms it, estimating that the world’s oceans contain over 250,000 tons of trash. This is about ten times more than other recent studies suggested.

Every day a staggering quantity of garbage, from plastic bottles to bags and, really, anything else is poured into the oceans. It reaches harbours and river mouths and from there it migrates in the remote stretches of the sea transported by gyres – large systems of circulating currents. One of the most tragic results of this is the formation of island of trash, such as the Great Pacific Garbage Patch – a trash-filled region of the Pacific Ocean the size of Texas.

Patch of floating ocean garbage (credit: Lindsey Hoshaw)

Patch of floating ocean garbage (credit: Lindsey Hoshaw)

In the 1970s, studies suggested that about 45,000 tons of plastic littered the ocean. The world’s production of plastic has increased fivefold since then. One of the problem with making a precise estimate is that it is very hard to establish just how much of the world’s plastic makes its way into the ocean and how long it lasts before fish, sunlight and currents break it down and carry it into the deep ocean. Up until now, the most reliable method was by visual assessment or by trawling the seas with nets.

The new study conducted by the US 5 Gyres Institute has tried to improve current assessing methodologies and improve our understanding of the dynamics behind plastic pollution of the ocean. One of the leading researchers Dr Markus Eriksen with his colleagues looked at ocean plastic estimates from 24 expeditions – drawing together the results of 680 surface net tows and 891 visual surveys – to all of the world’s five gyres, from Iceland to the Bay of Bengal. The novelty in their investigation lays in the integration of visual surveys and net hauls with mathematical models for how ocean circulation determines the transport of plastic. The first ‘highly conservative’ estimate suggests that there are about 5.25 trillion plastic pieces afloat on the global oceans, for a total mass of roughly 269,000 tons. Unfortunately, as Dr Eriksen points out, the ‘garbage patches’ are not the final resting places for the plastic. The study in fact, did not take into consideration potentially large amounts of plastic floating deeper in the water, on the seabed, or cast ashore.

Although “The status quo is not acceptable” – Dr Eriksen said, he maintains a certain optimism adding that if – and that is a big ‘if’ – people stopped adding to the problem with throw-away plastic the oceans will eventually clean themselves.

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Carlo Bradac

Carlo Bradac

Dr Carlo Bradac is a Research Fellow at the University of Technology, Sydney (UTS). He studied physics and engineering at the Polytechnic of Milan (Italy) where he achieved his Bachelor of Science (2004) and Master of Science (2006) in Engineering for Physics and Mathematics. During his employment experience, he worked as Application Engineer and Process Automation & Control Engineer. In 2012 he completed his PhD in Physics at Macquarie University, Sydney (Australia). He worked as a Postdoctoral Research Fellow at Sydney University and Macquarie University, before moving to UTS upon receiving the Chancellor Postdoctoral Research and DECRA Fellowships.

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