What happens to plastic in the ocean?

Article by Isabel Key and Mina Frost.

So far, we have produced 8.3 billion tons of plastic [1], 40% of which was used for packaging [2]. That’s over a ton of plastic per person alive today [7]. How much of it ends up in the ocean? And what happens to it then?

Of the 8.3 billion tons of plastic produced, 6.3 billion tons are now waste [1]. Only 9% of that has been recycled, 12% has been burnt, and the other 79% still exists somewhere in its original form [1]. For 8 million tons of plastic a year, this “somewhere” is the ocean [5]. This is like emptying one garbage truck of plastic into the ocean every minute [3]. Plastic pollution has increased 10-fold since 1980 [17]. If we continue to dump plastic into the ocean at an increasing rate, it may weigh more than all marine fish by 2050 [3].

Some ocean plastic is eaten by animals – why? Plastic usually doesn’t look like food to us humans, but there can be ‘sensory traps’ which trick animals into eating plastic [11,18]. We’ll explain one example:

Plastic tends to congregate in patches in the ocean, due to currents [10]. Lots of phytoplankton (like tiny marine plants) grow on the plastic, and release chemicals which larger animals smell from far away [11]. These chemicals attract animals like albatrosses (big white birds) to the plastic, because the chemicals usually indicate a source of food [12], likely resulting in them eating plastic by mistake [11].

But how long does it take for the plastic to disappear? Plastic doesn’t usually naturally biodegrade [15]. It can only be broken down into smaller pieces [16] or destroyed by the sun’s UV light [14], which can take hundreds or even thousands of years [6,13]. Plastic in the deep ocean takes a particularly long time to degrade, due to there being very little light and oxygen [13]. Microplastics (small pieces) are almost impossible to remove from the ocean, and if not broken down, will be buried in the seabed and form part of the fossil record [4,9]. People in the future may look back at us as the age of plastics, or the ‘Plasticene’ [8].

References

[1] https://advances.sciencemag.org/content/3/7/e1700782.full

[2] https://www.mdpi.com/2313-4321/3/1/1

[3] https://www.ellenmacarthurfoundation.org/assets/downloads/EllenMacArthurFoundation_TheNewPlasticsEconomy_Pages.pdf

[4] https://www.sciencedirect.com/science/article/pii/S0269749113005642

[5] https://theconversation.com/eight-million-tonnes-of-plastic-are-going-into-the-ocean-each-year-37521

[6] https://www.alansfactoryoutlet.com/how-long-does-it-take-plastics-to-break-down

[7] https://www.worldometers.info/world-population/

[8] https://www.newscientist.com/article/mg22530060-200-plastic-age-how-its-reshaping-rocks-oceans-&-life/

[9] https://scripps.ucsd.edu/centers/cmbc/2018/12/12/the-problem-of-micro-&-macro-plastic/

[10] https://www.pnas.org/content/111/28/10239.short

[11] https://advances.sciencemag.org/content/2/11/e1600395?utm_source=VancePak+(updated+11%2F4)&utm_campaign=76ca0566fd-EMAIL_CAMPAIGN_2016_11_04&utm_medium=email&utm_term=0_56c46682ac-76ca0566fd-126550997

[12] https://academic.oup.com/icb/article/51/5/819/629679

[13] https://royalsocietypublishing.org/doi/full/10.1098/rstb.2008.0205?casa_token=SMdCAWHCsDoAAAAA:TSp90mVacIkMgKJEn0y-AWJ4bE0SPjGZaKZVJN2YhO1II7TEx42CUvLli57eDn32xvcEnru85KSHU68

[14] https://www.sciencedirect.com/science/article/pii/S0025326X10003553

[15] https://science.howstuffworks.com/science-vs-myth/everyday-myths/how-long-does-it-take-for-plastics-to-biodegrade.htm

[16] http://epubs.surrey.ac.uk/844843/1/Channelling%20passion%20for%20the%20ocean%20towards%20plastic%20pollution.pdf

[17] https://knowledge.unccd.int/publications/ipbes-2019-global-assessment-report-biodiversity-&-ecosystem-services

[18] https://www.researchgate.net/publication/226474190_The_roles_of_sensory_traps_in_the_origin_maintenance_&_breakdown_of_mutualism

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This post is inspired by “Kurzgesagt”: https://www.youtube.com/watch?v=RS7IzU2VJIQ

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