Microplastics are classified as pieces of plastic less than 5mm in diameter, and include microplastic fibers and microplastic beads. These minute particles come from products and clothing we use everyday and ultimately find their way to the ocean where they have detrimental effects on the animals that live there.
When a piece of clothing made from synthetic material (nylon, acrylic, polyester, etc) is washed in a washing machine, tiny fibers of that material are shed from the clothing into the water. From your washing machine, these plastic microfibers find their way into the sewer system where they then go through sewage treatment plants, passing through the filtration systems and into rivers and lakes which in turn flow into the ocean. Similarly, when cosmetic products or face washes containing microplastic beads are used, the beads find their way from your sink to the ocean. Plastics also make their way into the ocean through the action of the wind or by being directly dumped.
Plastics in the ocean accumulate mainly along the coast, where a large percentage of the human population lives, and in oceanic gyres. Gyres are large systems of circulating ocean currents caused by the Earth’s rotation. There are five major gyres across the world: The Indian Ocean Gyre, North and South Atlantic Ocean Gyres, and the North and South Pacific Ocean Gyres. Plastics get caught in these major currents and become trapped, forming major aggregations such as the Great Pacific garbage patch, found in the North Pacific Gyre. With all of this plastic floating in the ocean, how does it interact with wildlife and zooplankton?
Zooplankton, such as copepods, that come into contact with microplastics often mistake them for food, as they can be the same size as their natural food. Once microplastics have been ingested they can reduce the amount of plankton copepods will eat, depriving them of precious energy, or they can cause complete blockages of the gut. Microplastic fibers can also become entangled around the antennae, legs and feeding appendages of copepods, hindering them from their natural behaviour. Another issue of zooplankton eating microplastics, is what happens when animals further up the food chain eat the zooplankton.
If an animal such as a fish eats a copepod (or other zooplankter) that has ingested microplastic, the fish also ingests that microplastic. These predator prey interactions work their way up the food chain, with those at the top, such as seabirds, seals, or whales accumulating larger loads of plastics in their digestive tracts. This is an example of bioaccumulation, and happens with other contaminates such as mercury.
Microplastics can degrade and leach chemicals into the animal which ingested them, which can cause endocrine disruption, which can have a negative impact on reproduction and development, mobility, or cause cancer. On top of releasing chemicals already found in them, microplastics can also absorb and release pollutants, adding further harm.
Governments have come to realize the threat microplastics pose, with Environment Canada beginning studies in 2015 of their impact on wildlife and the environment. In 2016 the federal government announced its plans to ban the sale of facial scrubs, shower gels, and toothpastes containing plastic microbeads, starting July 1, 2018. Microbeads in non-prescription drugs and natural health products will be banned July 1, 2019. It’s heartening to see that steps are being taken to tackle this problem, but there’s still a long way to go before plastics are eliminated from the world’s oceans.
Cole, M., Lindeque, P., Halsband, C., Moger, Galloway, T., 2011. Microplastics as contaminants in the marine environment: A review. Marine Pollution Bulletin. 62:2588-2597
Cole, M., Lindeque, P., Fileman, E., Halsband, C., Goodhead R.M., Moger, J., Galloway, T., 2013. Microplastic ingestion by zooplankton. Environmental Science & Technology. 47(12):6646–6655
Wright, S.L., Thompson, R.C., Galloway, T.S., 2013. The physical impacts of microplastics on marine organisms: A review. Environmental Pollution. 178:483-492
Desforges, J.W., Galbraith, M., Ross, P.S., 2015. Ingestion of Microplastics by Zooplankton in the Northeast Pacific Ocean. Archives of Environmental Contamination and Toxicology. 69(3):320-330
Oregon State University, https://www.flickr.com/photos/oregonstateuniversity/21282786668, Featured Image (Microplastics)