When most people hear the words “plastic pollution”, images of a derelict soda bottle or passively floating shopping bag probably cross their mind. However, the ocean’s plastic problem is a lot “bigger” than left-behind bottles. Presently, much of the plastic in the ocean and on our beach shores is termed microplastics, or plastic fragments that are too small to be easily seen with the naked eye.
Microplastic is currently a buzzword in both the media and science. But just what is a microplastic? According to National Ocean and Atmospheric Administration (NOAA), a microplastic is any plastic particle that is less than 5 mm in size (1). For reference, the eraser on basic yellow pencil is 5 mm. Because they are so small, a microscope or instrumentation like Fourier Transform Infrared Spectroscopy (which measures the way different plastics absorb infrared radiation) is needed in order to even see these plastic pieces (2). Additionally, some researchers have found they are limited in what size ranges they can detect due to their sampling equipment; for example, if ocean water is filtered through a 1 micrometer mesh net, any microplastics less than 1 micrometer pass through back into the ocean, never getting the chance to be counted (3)!
Microplastics are created in a few different ways. Perhaps the most common is from the breakdown and fragmentation of larger plastic pieces, called weathering (2). A plastic lunch bag tossed on the ground is likely to get fragmented into smaller and smaller pieces by processes including photodegradation (sunlight), thermo-oxidation (slow breakdown caused by moderate temperatures), and even biological decomposition (4). Alternatively, some plastics are manufactured to be tiny and can be classified as microplastics without any further fragmentation. These include nurdles, which are the “raw material” phase of industrial plastics consisting of tiny plastic pellets, microbeads found in facial exfoliators, and synthetic fibers from clothes.
How many microplastics are in the ocean?
The invention of plastic has certainly made modern day life more convenient! However, we sure do produce and use a lot of it. As of 2011, the global demand for plastic was ~245 million tonnes with one third of that being single use items (4). Unfortunately, this implies that plastic pollution will be an issue for years to come.
It is hard to fully pin down how many microplastics are in the ocean, or washed up on your favorite beach. A recent study estimated that 4.85 trillion pieces of microplastics are floating in the world’s ocean, which make up 92.3% of the total quantity of plastic in the surface of the ocean (5). Concentrations of microplastics have been measured as high as 100,000 particles per cubic meter in a Swedish harbor (1).
As you would expect, there is a strong relationship between nearby population and how many microplastics end up in the coastal sediments. Every once in a while, you may hear the rumor that marine plastics are all from abandoned fishing gear; however, it is now better understood that ~80% of marine microplastics originated from land (4). In other words, our litter makes up most of that ocean’s plastic problem!
Plastic for dinner?
Okay, fine, there are a bunch of tiny plastic pieces in the ocean…so what?
One of the main problems with microplastics is their size! Many microplastics happen to be the same size as plankton, the base of the aquatic food web. In other words, marine critters can mistake a plastic piece as a tasty phytoplankton cell. Clear and white plastics, the most popular colors, have similar coloration to many plankton species. A visible predator, like some shrimp, will often mistake microplastics for food (1). When eaten, some planktonic organisms such as the water flea, have significantly slower swimming rates when microplastics are ingested!
If you enjoy eating anything from the ocean, microplastics should be a relevant topic. For example, bivalves, such as mussels and oysters, are filter feeders, which means they could easily uptake microplastics and pass them on to you if eaten. Europeans who enjoy shellfish are estimated to consume 11,000 plastics particles a year.
Oh, you’re a vegetarian? A recent study from China found that table salt contained 7 to 681 plastic particles per kilogram of salt.
One of the greatest concerns of ingesting microplastics is the potential exposure to harmful organic pollutants. Organic pollutants “stick” to plastics in a process called sorption during the plastic creation process (think BPAs) and additionally while in the environment. For example, a PCB molecule dissolved in the water would much prefer to be sorbed to a microplastic (6). Once ingested, a microplastic can transfer that organic pollutant to its consumer, which can then be passed up the food web.
Interestingly, in 2005, International Pellet Watch was launched, which uses plastic nurdles for good. Persistent organic pollutants can be extracted from the plastic beads that wash up on beaches to give scientists a basic understanding of the organic pollutant levels in coastal bays. That’s pretty cool!
What can you do?
This is a hotly debated issue because there is no easy solution to getting rid of microplastics. However, if we work together as a community, we can make a huge difference.
The first, and most obvious, is to make efforts to reduce the plastic we add to the ocean. Reduce, re-use, and recycle! For example, use fabric or re-usable bags next time you go grocery shopping or try a canteen instead of buying a plastic bottle of water.
Another recommendation is to use only natural exfoliators. Those tiny blue microbeads found in many facial washes are the same size as plankton (6). Good news, microbeads have been banned in the US and Canada and will be phased out by July 2017 and will stop being sold in stores starting July 2018. So until 2018, opt for an exfoliator that uses sugar crystals or crushed nut shell.
Additionally, you could participate in a beach clean-up. Many non-profit organizations (such as the Ocean Conservancy and the Surfrider Foundation), universities, and local communities organize clean-up events. It’s a great way to meet new people and help make your favorite beach ready for summer! There are other efforts that reuse plastics beyond recycling, such as for art, clothing, and even as garden planters!
Plastics are wonderful and have made life cheaper and easier in many cases. However, the cost of this advancement is now being seen in our oceans. Awareness that what we throw away doesn’t always just go away is the best advice we can bestow. At the very least, never litter. As an environmentalist, I like to think people know not to throw trash on the ground; however, as rumor has it, when Walt Disney was designing his theme park, he found that the average person will only take 30 steps before they litter (which is why there are so many trash cans in Disney World).
So today, if you see a piece of plastic, throw in in a recycle bin, even if you have to walk more than 30 steps!
Works Cited (and great reads!)
(1) Wright, Stephanie L., Richard C. Thompson, and Tamara S. Galloway. “The physical impacts of microplastics on marine organisms: a review.” Environmental Pollution 178 (2013): 483-492. DOI:10.1016/j.envpol.2013.02.031
(2) Kershaw, P. J. “Sources, Fate and Effects of Microplastics in the Marine Environment: A Global Assessment.” Rep. Stud. GESAMP 90 (2015): 96.
(3) Hidalgo-Ruz, Valeria, et al. “Microplastics in the marine environment: a review of the methods used for identification and quantification.” Environmental science & technology 46.6 (2012): 3060-3075. DOI: 10.1021/es2031505
(4) Andrady, Anthony L. “Microplastics in the marine environment.” Marine pollution bulletin 62.8 (2011): 1596-1605. DOI:10.1016/j.marpolbul.2011.05.030
(5) Eriksen, Marcus, et al. “Plastic pollution in the world’s oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea.” PloS one9.12 (2014): e111913. DOI: 10.1371/journal.pone.0111913
(6) Fendall, Lisa S., and Mary A. Sewell. “Contributing to marine pollution by washing your face: Microplastics in facial cleansers.” Marine pollution bulletin 58.8 (2009): 1225-1228. DOI:10.1016/j.marpolbul.2009.04.025