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The Microplastic Problem

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By Megan Buras, SRC intern

Figure 1: Plastic products are ubiquitous in our lives and the environment (Photo via Tanvi Sharma on Unsplash)

Today plastic is everywhere, from grocery stores to health products and even the shoes on our feet. The massive amount of plastic used daily, and its improper disposal have led to the accumulation of these plastics in the environment. Once plastic debris enters the ocean, it “breaks down into microplastics by photolytic, mechanical and biological degradation” (Alfaro-Núñez et al. 2021). These microplastics cause a wide range of issues, including ingestion by filter feeders mistaking this debris for plankton. One study reported “that 26%–52% of the fish collected in the English Channel had plastic debris in their gut” (Silva-Cavalcanti et al. 2017). The accumulation of microplastics in the environment has reached a point where it has begun to impact the species that live there. A study published in 2021 focused on the Tropical Eastern Pacific and Galápagos archipelago collected 240 samples from 16 different marine species. They found microplastic particles in 100% of the samples (Alfaro-Núñez et al. 2021). Species are now commonly encountering and ingesting microplastics. So what does this mean, and why is this an issue? In terms of the species that are primarily ingesting these microplastics, it has been found to cause intestinal issues, reduce nutrient absorption, and even impact fish metabolism and interfere with their immune system’s responses (Lu et al. 2016, Silva-Cavalcanti et al. 2017). Fish species that humans commonly consume have been found to contain microplastics, but little research has been done on how microplastic consumption affects humans.  

Fish and aquatic products make up a significant portion of the diet of many people globally. The amount of global aquatic animal food production has “increased over threefold from 40.8 million tonnes in 1970 to 128 million tonnes in 2010”(Tacon and Metian 2013). It is evident that fisheries play an important role in global food security. This demand for increased aquatic food production has led to damaging and catastrophic effects on the global fish stocks, threatening the food security of the world while trying to meet its demands. The rise of aquaculture has also been significant but comes with its own series of challenges in terms of what is used to feed the fish as well as disease management and resource usage. 

Figure 2: Commercial fishing has been found to have an important connection to microplastic pollution (Photo via Megane Delhaie on Unsplash)

On top of all that information, a study has found that commercial fishing contributes significantly to microplastic pollution. Results from the study “showed that the dominant contaminants (polypropylene fibers and polyethylene fibers) might originate from the abrasion of fishing gear and contributed to 61.6% of the total abundance of microplastics in surface sediment”(Xue et al. 2020). Overfishing and microplastic pollution are connected in more ways than previously thought. This begs the question: How can we better manage global fisheries productively and efficiently without compromising microplastic pollution?

Figure 3: Global food security depends on the stability of fish stocks and proper management (Photo via David Todd McCarty on Unsplash)

Looking to the future, what can be done to reduce microplastic accumulation in the environment? Reducing the demand for plastic-packaged products and plastic microbeads could potentially cut off the source of plastic debris. Better regulation and disposal of plastic could limit the amount entering the ocean and environment. What can be done to protect fisheries? More effective management of commercial marine fisheries to sustain the global fish stocks for future generations. And, of course, more research into the effects of microplastic ingestion in humans would be an excellent place to start too.

 

Works cited

Alfaro-Núñez, A., D. Astorga, L. Cáceres-Farías, L. Bastidas, C. S. Villegas, K. Macay, and J. H. Christensen. 2021. Microplastic pollution in seawater and marine organisms across the Tropical Eastern Pacific and Galápagos. Scientific reports 11:1-8.

Lu, Y., Y. Zhang, Y. Deng, W. Jiang, Y. Zhao, J. Geng, L. Ding, and H. Ren. 2016. Uptake and accumulation of polystyrene microplastics in zebrafish (Danio rerio) and toxic effects in liver. Environmental science & technology 50:4054-4060.

Silva-Cavalcanti, J. S., J. D. B. Silva, E. J. de França, M. C. B. de Araújo, and F. Gusmão. 2017. Microplastics ingestion by a common tropical freshwater fishing resource. Environmental pollution 221:218-226.

Tacon, A. G., and M. Metian. 2013. Fish matters: importance of aquatic foods in human nutrition and global food supply. Reviews in fisheries Science 21:22-38.

Xue, B., L. Zhang, R. Li, Y. Wang, J. Guo, K. Yu, and S. Wang. 2020. Underestimated microplastic pollution derived from fishery activities and “hidden” in deep sediment. Environmental science & technology 54:2210-2217.

Plastic debris contamination in the Acoupa weakfish (Cynoscion acoupa) in a tropical estuary

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By Elana Rusnak, SRC intern

The Acoupa weakfish (Cynoscion acoupa) is an economically important fish that lives along the tropical east coast of the American continents. They tend to live in estuary systems—calm, brackish water habitats—as juveniles and sub-adults, and then move to saltier areas as they age. Tropical estuaries are one of the most productive ecosystems on Earth, and they provide shelter, food, and developmental grounds for many species of fishes and invertebrates. Unfortunately, since estuaries are more sheltered environments, plastic debris tends to accumulate and be ingested by the many species that make the estuary their home.   A study by Ferreira et al. in 2016 explored the feeding habits of all life stages of the Acoupa weakfish in the Goiana Estuary in Brazil, and described the plastic debris contamination of the area and how it affects these economically important fish.

In this study, the fish were subdivided into three study groups: juvenile, sub-adult, and adult. They were observed and captured in the upper, middle, and lower parts of the Goiana Estuary, with the lower part being the saltiest. About 470 juveniles, 25 sub-adults, and 33 adults were used in this study. The stomach contents of each fish were removed and examined to determine the ratio of plastic debris to their natural diet (fish, crustaceans, worms, seaweed, plant fragments). The researchers found that in almost every fish, the majority of the stomach contents consisted of plastic debris, followed by crustaceans and fish (64.4% of juveniles, 50% of sub-adults, and 100% of adults were contaminated with plastic). Multicolored plastics were also found in the digestive tract, and a few specimens had nothing in the stomach other than plastic debris.

Plastic debris inside a penaeid shrimp, a primary food source for adult Acoupa weakfish (Ferreira et al., 2016)

Plastic debris inside a penaeid shrimp, a primary food source for adult Acoupa weakfish (Ferreira et al., 2016)

 

Zoomed in image of red plastic debris inside the digestive tract of an Acoupa weakfish specimen (Ferreira et al., 2016)

Zoomed in image of red plastic debris inside the digestive tract of an Acoupa weakfish specimen (Ferreira et al., 2016)

 

So what does this all mean?

First, the Goiana Estuary waters are polluted with plastic debris at densities comparable to half the density of the fish larvae that reside in it (Lima et al., 2015). This indicates that this estuary system is very polluted. Moreover, the Acoupa weakfish isn’t the only organism ingesting all this plastic. The direct ingestion of plastic debris might primarily occur during the early stages of the Acoupa weakfish, whereas sub-adults and adults ingest debris through the trophic food chain (their prey ingests the plastic, then it is left behind in the adult fish’s stomach). This occurs through a process called biotransferrence. The presence of plastic in the digestive system is also problematic, as it can lead to digestive injuries and induce starvation. Since the Acoupa weakfish is a top predator in their estuarine habitat, they are more susceptible to food web disturbances.

This fish is not only a primary food source for the locals in the area, but it is also commercially fished. If they are filled with plastic, they are not getting the nutrition they need to become large, healthy fish. Without this growth, both the locals and the commercial industry will suffer. This study really showed the large-scale change that needs to begin now with regards to reducing plastic waste and keeping our environment clean and healthy.

Works cited

Ferreira, G.V.B., Barletta, M., Lima, A.R.A., Dantas, D.V., Justino, A.D.S., Costa, M.F. 2016. Plastic debris contamination in the ife cycle of Acoupa weakfish (Cynoscion acoupa) in a tropical estuary. ICES Journal of Marine Science 73: 2695-2707.

Lima, A. R. A., Barletta, M., and Costa, M. F. 2015. Seasonal distribu- tion and interactions between plankton and microplastics in a tropical estuary. Estuarine, Coastal and Shelf Science, 161: 93–107.