The Plastic Predicament: Uncovering the True Extent of Ocean Pollution

Written by: Jon Zhang '24
Edited by: Melinda Li '22

If you care about the environment, you’ve likely heard of the Great Pacific Garbage Patch (GPGP), a collection of trash more than twice the size of Texas floating in the Pacific Ocean. Carried by winds and ocean currents, plastic debris accumulates at the surface of the ocean, and the GPGP grows larger each day [1].

The GPGP spans over 600,000 square miles and consists of roughly 1.8 trillion pieces of plastic weighing over 88,000 U.S. tons [1]. While these numbers already seem staggering enough, this only accounts for about 1% of all plastic that has ever entered the ocean [2]. It is mind-boggling enough to visualize a gigantic mass of plastic floating in the ocean, but this is only a small contributor to the sheer extent of marine pollution. 

So where does the rest of the plastic end up? For starters, some of the plastic degrades or simply sinks to the ocean floor. Around 40% of plastic is denser than seawater, and these plastics sink, remaining largely intact. Other items get broken down into microplastics, which account for roughly 94% of the 1.8 trillion pieces of trash floating in the GPGP [3]. A study conducted off the coast of California used relative dating to investigate the presence of microplastic, with bottom layers of ocean sediment corresponding to older dates of origin and vice versa. The researchers found an exponential increase of microplastic in layers dated from 1945-2009, doubling every 15 years. In addition to sediment deposition, aquatic animals such as plankton can ingest these plastic fragments. Small pieces of plastic block digestive tracts, making feeding more difficult. Plastic also contains organic pollutants like polycyclic aromatic hydrocarbons that are harmful to organisms, potentially causing liver toxicity and brain damage. Furthermore, when smaller animals are consumed by larger animals, plastic in their bellies can impact many more organisms as it works its way up the food chain [4]. 
However, in many cases, plastics in the ocean end up much closer to shore. Sadly, beaches littered with plastic washed ashore by waves are not uncommon sights.  Scientists suspect that the majority of plastic trash sticks closer to land than we imagine. Erik van Sebille, a Dutch oceanographer, leads a research project studying how marine plastic travels. The research team created virtual models of water currents to determine where simulated plastic would end up. Van Sebille believes that the bulk of plastic remains within 100 miles of coastline, repeatedly being carried away by waves and washing up again on beaches, with just a few items making it to the open ocean [5]. 

This conclusion is supported by examining the production dates of various items found in the GPGP. Much of the plastic floating in the GPGP was manufactured before the 1990s, with the oldest discovered item, a plastic crate from Taiwan, originating from 1971 [5, 6]. If plastic just sank to the bottom of the ocean, pollution near the surface should be newer, with older plastic having already sunk. A 2019 study, whose authors include the founder and head researcher at The Ocean Cleanup organization, used a computer box model to conclude that recently-manufactured plastic debris mainly circulates between coastal areas [6]. 

Together, these theories illustrate the persistence and pervasiveness of this issue. The GPGP poses a serious problem by itself, but unfortunately, plastic floating near the ocean’s surface represents just a tiny fraction of total marine pollution. These explanations for the “missing” plastic might sound simple, but they paint a more comprehensive picture of how far humanity has tampered with its aquatic ecosystems. 

So while organizations such as The Ocean Cleanup are doing important work of studying and cleaning up the GPGP, more effective solutions begin with us on land. Instead of boating into the middle of the Pacific, participating in beach cleanups are more impactful (and easier!). But ultimately, the simplest solution is prevention. Once plastic makes its way into the environment - whether buried in sea sediment, swallowed by marine organisms, or washed up on beaches - it becomes difficult to remove, not to mention the hundreds of years it takes to decompose naturally. Humanity must recognize the legacy of modern life and its imprints upon the planet, beginning with plastic. 

Works cited:

[1] Rice D. World's largest collection of ocean garbage is twice the size of Texas [Internet] [Cited 2021 April 24]. Available from: https://www.usatoday.com/story/tech/science/2018/03/22/great-pacific-garbage-patch-grows/446405002/ 

[2] Kormann C. Where Does All the Plastic Go? [Internet] [Cited 2021 April 24]. Available from: https://www.newyorker.com/news/news-desk/where-does-all-the-plastic-go 

[3] Lebreton L, Slat B, Ferrari F, Sainte-Rose B, Aitken J, Marthouse R, et. al. Evidence that the Great Pacific Garbage Patch is rapidly accumulating plastic. Scientific Reports [Internet]. 2018 [Cited 2021 April 24]; 8(4666), 1-15. DOI: https://doi.org/10.1038/s41598-018-22939-w 

[4] Brandon JA, Jones W, Ohman MD. Multidecadal increase in plastic particles in coastal ocean sediments. Science Advances [Internet]. 2019 [Cited 2021 April 24]; 5(9), 1-6. DOI: https://doi.org/10.1126/sciadv.aax0587 

[5] Vox. Why 99% of ocean plastic pollution is "missing" [Internet] [Cited 2021 April 24]. Available from: https://www.youtube.com/watch?v=fsjvwQclGLo 

[6] Lebreton L, Egger M, Slat B. A global mass budget for positively buoyant macroplastic debris in the ocean. Scientific Reports [Internet]. 2019 [Cited 2021 April 28]; 9(12922), 1-10. DOI: https://doi.org/10.1038/s41598-019-49413-5 

[Image Citation] Oliveira P. Plastic garbage floating in the ocean. Unlike organic debris, which biodegrades, the photo degraded plastic disintegrates into smaller and smaller [Internet] [Cited 2021 April 24]. Available from: https://www.alamy.com/plastic-garbage-floating-in-the-ocean-unlike-organic-debris-which-biodegrades-the-photo-degraded-plastic-disintegrates-into-smaller-and-smaller-image214892605.html