Microplastics in Fish: Not a Microproblem

Plastics are everywhere. We humans use them in everything – from toys to food packaging to medical supplies and beyond. As a manmade material, plastics do not readily break down in the environment once we are finished using them. To make matters worse, there is an abundance of teeny, tiny pieces of plastics in our world. These tiny bits can occur as a byproduct of the production of plastic goods, or they may be a result of litter in the environment breaking down into smaller and smaller pieces (Barboza et al., 2020). Because they are so small, they spread easily. Today, little pieces of plastic are found everywhere: in our soil, on our beaches, in rivers and oceans, and even scarier… inside the bodies of animals.

“Microplastic” by Oregon State University is marked with CC BY-SA 2.0. To view the terms, visit https://creativecommons.org/licenses/by-sa/2.0/?ref=openverse

These miniscule bits of plastic measuring less than 5 mm are also known as microplastics, and they truly are ubiquitous in today’s environment. (So much so that they are now considered a contaminant of concern on a global scale (Barboza et al., 2020).) Ingestion of microplastics has been documented in over 700 marine animal species, including sea turtles, whales, dolphins, and fish (Wootton, 2021). This either happens when animals mistake microplastics as food and ingest them by accident, or they ingest another smaller prey organism that also has microplastics inside of its body (Wootton, 2021). Fish may also take in microplastics passively as they filter contaminated water through their gills. As a result, microplastics have been found in the digestive tracts, muscle tissues and even the gills of fish (Barboza et al., 2020).

So why should we care if fish are accumulating small particles of plastic in their bodies? Recent studies have demonstrated that there are multiple toxic impacts of microplastic ingestion in fish. These impacts include impaired development, decreased feeding and body mass (Naidoo and Glassom, 2019), damage to cells, changes in behavior, impaired reproductive capacity, and even death (Barboza et al., 2020). There are documented instances of neurotoxicity (or damage to the nervous system) as a result of microplastic ingestion in fish. Oxidative stress, or an imbalance of antioxidants and free radicals in the body, has also been found to result from accumulation of plastics in the body, and may lead to cell and tissue damage in fish (Barboza et al., 2020). All of these impacts have the potential to harm the overall population of a particular species of fish, and ultimately alter food webs.

Conceptual model illustrating capture, retention and internalization of microplastics by fish species (Barboza et al., 2020).

If none of that grabbed your attention, perhaps this will: since microplastics have been found in the edible muscle tissues of fish, humans are also at risk of accumulating small bits of plastic in their bodies after eating a fish meal. Further studies into human risk assessment of microplastic ingestion are warranted, and perhaps microplastic daily intake limits may be in our future once the research is more solid (Barboza et al., 2020). Also, if food webs are altered enough by reduced populations of fish impacted by microplastics, maybe your favorite type of fish will be a lot harder to come by in the grocery store years down the line. For now, take note next time you are on a walk around your neighborhood and see the tiny pieces of a broken up plastic bottle cap – think about the impacts to the fish in a nearby waterway once a heavy rain washes those microplastics downstream. If nothing else, perhaps this thought will motivate each of us to choose to use less plastic in some capacity in our daily lives.

 

References:

Barboza LG, Lopes C, Oliveira P, Bessa F, Otero V, Henriques B, Raimundo J, Caetano M, Vale C and Guilhermino L. (2020) Microplastics in wild fish from North East Atlantic Ocean and its potential for causing neurotoxic effects, lipid oxidative damage, and human health risks associated with ingestion exposure. Science of the Total Environment 717:1-14.

Naidoo T and Glassom D. (2019) Decreased growth and survival in small juvenile fish, after chronic exposure to environmentally relevant concentrations of microplastic. Marine Pollution Bulletin 145:254-259.

Wootton N, Reis-Santos P and Gillanders BM. (2021) Microplastic in fish – A global synthesis. Rev Fish Biol Fisheries 31:753-771.