Marine Microplastics: Not a small problem, despite its name
Plastic use and resulting pollution have become critical and seemingly uncontrollable consequences of human activity in recent years. Although sustainable reusable products have started to flood the market highlighting the dangers of relying on single-use plastic items, plastics are still being produced, used, and discarded every day around the world.
A majority of plastics that are not burned in a landfill or properly recycled find their way into the ocean. Whether it’s the cap from your sports drink, a plastic shopping bag, or even plastic fibers from your clothes in the wash, the plastics will end up in the ocean. Nearly 70% of worldwide marine debris are plastics, with an astounding 4.8-12.7 million tons of plastics added each year. Even in the most remote corners of the ocean, hundreds of miles from human civilization, plastics accumulate. This is because of the strength of ocean currents, churning the waters and carrying plastics thousands of miles. Unfortunately, plastics degradation can take anywhere from 500-1000 years, so nearly all plastic ever created still exists.
Research on the topic
There is unwavering support that ocean plastics are a major problem but to date there is no consensus on how to measure the total amount of plastics in our oceans. In part, this is because of microplastics. Microplastics are small plastic particles, nearly impossible to see with the naked eye (less than 5mm) that come from weathered large plastics, clothing fibers, road tires, and city dust, among other sources. Microplastics are transported quickly into the marine environment through wastewater, road runoff, even wind, making microplastic pollution an ever-growing problem.
Microplastics, being as tiny as they are, may seem like a less critical issue than larger plastics typically pictured on ocean clean up campaigns. Microplastics have been gaining recent attention among marine researchers because of their ability to quickly make their way into marine food web and cause significant health problems for many organisms. Microplastics are almost indistinguishable from krill, eggs, plankton, or other protein-rich organisms that countless species rely on for food. When microplastics are ingested by a marine species they can easily lodge themselves in stomachs or digestive tracts, causing organisms to feel full but gain no nutrition. Microplastics can also become a home for rare marine microbes that can utilize the carbon stored in the microplastics, making these marine microbes threatening to the the microbiome of any species that ingests it.
How can scientists help?
To help understand the impacts of microplastics on marine ecosystems, discovering new ways to monitor and study their breadth and accumulation will be crucial. In a research project published in 2019 by Dr. Randi Rotjan et al. the team asked questions about the ingestion of microplastics by the northern star coral, Astrangia poculata. A. poculata has been commonly used as a bioindicator of water quality because of its large range, from the east coast of the United States to the Gulf Coast, and even Bermuda. Therefore, the authors investigated if A. poculata can be used as a case study to determine the effect of microplastics on ingestion patterns and ecosystem health.
Using tracking techniques and measurements both in the wild and in the lab, the authors found that A. poculata not only consumed microplastics frequently in the wild but preferred microplastics to their common prey, brine shrimp eggs. The corals found with microplastics accumulation had mostly small fibers lodged into internal tissues, while the coral demonstrated the ability to successfully egest the larger microplastic beads. In the lab, A. poculata ingested microplastics coated with microbial Escherichia coli almost immediately, confirming fears that microbiomes could easily be altered with the ingestion of biofilm microplastics.
Surprisingly, A. poculata appeared resilient to microplastic ingestion and could survive in the wild with internal accumulation of microplastics. With its wide geographic range and demonstrated ability to survive with internal plastics, A. poculata could serve as an important indicator for microplastic accumulation across its extensive habitat. These results bring us one step closer to understanding how microplastic pollution in our oceans affects marine life. While we can’t stop all plastic pollution, production, and use overnight, research like this help might push policy makers and industry in a plastic-free direction.
Original publication:
Rotjan, R.D., Sharp, K.H., Gauthier, A.E., Yelton, R., Baron Lopez, E.M., Carilli, J., Kagan, J.C., Urban-Rich, J. (2019). Patterns, dynamics, and consequences of microplastic ingestion by the temperate coral, Astrangia poculata. Proc. R. Soc. B 286: 20190726. https://royalsocietypublishing.org/doi/10.1098/rspb.2019.0726
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