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An Ocean of Microplastic

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Blog post by: Dr. Alena Pribyl

Plastic is hard to escape; from food and beverage containers to packaging to household items to clothing – it is everywhere in our society.  Despite efforts at recycling, much of this plastic is discarded and ends up in waterways and eventually the oceans.  It is estimated approximately 8 million metric tons of plastic enter the ocean annually1! But what happens to this plastic once it is in the ocean and how does it affect the marine ecosystem?

The dangers of large plastic debris in the oceans are well known – it can kill marine life through entanglement or ingestion. Sea turtles eat plastic bags, seabirds ingest small plastic pieces, fish and marine mammals become entangled in discarded fishing nets and rope. But another danger of marine plastic that we are just starting to understand is the effect of this plastic once it breaks down.  As large plastic pieces are exposed to UV radiation and wave action, they are eventually ground up into smaller and smaller pieces, called microplastics.

Where do microplastics come from?

microplastic

Microplastics are defined as pieces of plastic less than 5mm in size. The main sources of microplastics are large plastic debris that are broken down as described above, and a product called microbeads.  Microbeads are tiny plastic beads found in items such as soaps, facial scrubs and toothpaste where they act as abrasives.  They are usually listed as “polyethylene” or “polypropylene.”  These microbeads get washed down our drains, pass through the sewer system because they are too tiny to be filtered out, and eventually end up in the ocean.

Additionally, scientists have recently discovered another plastic source that is becoming more common in our oceans: plastic fibers from nylon and polyester fabrics.  These come off of clothes during washing, and similar to microbeads, pass through wastewater treatment systems to enter the ocean.

The dangers of a plastic diet

Once microplastics are in the ocean, filter-feeding animals often mistake them for food since they are the perfect size to ingest.  This includes animals such as  zooplankton (microscopic animals that drift in the sea and form the base of the marine food web), forage fish (e.g. sardine, herring),  shellfish (e.g. oysters, mussels), and even large marine mammals such as baleen whales.

 

A diet of plastic is no good for animals because microplastics also contain organic toxins such as polychlorinated biphenyls (PCBs), petroleum compounds, and even pesticides2. Some of these compounds are added to the plastics during manufacture, but many are picked up from the surrounding seawater.

Interesting fact: plastics are really good at taking up chemical “hitchhikers” that are present in low amounts in almost all water bodies. These chemicals are ingested along with the microplastic3.

Chemical-laden microplastics are not immediately lethal to marine animals, but cause problems over long periods of time. Growing evidence shows microplastic toxins accumulate in the tissues of marine organisms4-6 and cause long-term health problems such as reduced reproduction and liver damage7,8.  And the effect is not limited to the animals that directly eat microplastics. When these organisms are eaten by something else (including us), the toxins are transferred to the consumer, allowing them to spread throughout the food web9. This means all consumers of marine life could be at risk from microplastic toxins.

Microplastic oceans

pollutionRecent estimates put the amount of microplastic debris floating in our oceans between 93,000 to 236,000 metric tons10.  Much of this plastic collects in areas of the ocean where currents converge in circular patterns, called gyres – the so called “garbage patches” of the ocean.

However, the distribution of microplastics is not limited to the gyres – microplastics have been found in almost every marine habitat in the world, including the Arctic and remote oceanic islands11.  The spread of microplastics are creating large problems for the health of our ocean ecosystem, many of which we have only started to recognize.

How you can help

The good news is that everyone can do something to help slow this growing problem. We can take action by following these simple measures to reduce the amount of plastic entering our oceans:

  • Avoid purchasing soaps, toothpastes and cosmetics that contain “polyethylene” or “polypropylene” in their ingredients list.
  • Purchase clothes made with natural instead of synthetic fibers
  • Reduce or eliminate your use of items with large amounts of plastic packaging.
  • Use re-usable food and beverage containers.
  • Recycle as much plastic waste as possible
  • Pick up plastic waste you see lying on the ground and participate in local beach/river clean-ups.
  • Let your friends and family know what plastics are doing to our ocean and encourage them to follow these measures as well!

 

References

1 Jambeck, J. R. et al. Plastic waste inputs from land into the ocean. Science 347, 768-771, (2015).

2 Teuten, E. L. et al. Transport and release of chemicals from plastics to the environment and to wildlife. Philosophical Transactions of the Royal Society B: Biological Sciences 364, 2027-2045, (2009).

3 Bakir, A., Rowland, S. J. & Thompson, R. C. Enhanced desorption of persistent organic pollutants from microplastics under simulated physiological conditions. Environ. Pollut. 185, 16-23, (2014).

4 Browne, Mark A., Niven, Stewart J., Galloway, Tamara S., Rowland, Steve J. & Thompson, Richard C. Microplastic Moves Pollutants and Additives to Worms, Reducing Functions Linked to Health and Biodiversity. Curr. Biol. 23, 2388-2392,

5 Chua, E. M., Shimeta, J., Nugegoda, D., Morrison, P. D. & Clarke, B. O. Assimilation of Polybrominated Diphenyl Ethers from Microplastics by the Marine Amphipod, Allorchestes Compressa. Environ. Sci. Technol. 48, 8127-8134, (2014).

6 Avio, C. G. et al. Pollutants bioavailability and toxicological risk from microplastics to marine mussels. Environ. Pollut. 198, 211-222, (2015).

7 Sussarellu, R. et al. Oyster reproduction is affected by exposure to polystyrene microplastics. Proceedings of the National Academy of Sciences 113, 2430-2435, (2016).

8 Rochman, C. M., Hoh, E., Kurobe, T. & Teh, S. J. Ingested plastic transfers hazardous chemicals to fish and induces hepatic stress. Scientific Reports 3, 3263,(2013).

9 Tanaka, K. et al. Accumulation of plastic-derived chemicals in tissues of seabirds ingesting marine plastics. Mar. Pollut. Bull. 69, 219-222,(2013).

10 Erik van, S. et al. A global inventory of small floating plastic debris. Environmental Research Letters 10, 124006 (2015).

11 Lusher, A. in Marine Anthropogenic Litter (eds Melanie Bergmann, Lars Gutow, & Michael Klages)  245-307 (Springer International Publishing, 2015).