Pollution of Our Oceans With Microplastics Might Be a Bigger Problem than We Thought

by | May 2, 2022 | Climate & Environment

The sticky biofilms that form on microplastics can harbor disease-causing pathogens and help them spread. Image: Tunatura/iStockPhoto

Pollution of Our Oceans With Microplastics Might Be a Bigger Problem than We Thought

by | May 2, 2022 | Climate & Environment

The sticky biofilms that form on microplastics can harbor disease-causing pathogens and help them spread. Image: Tunatura/iStockPhoto
New research suggests disease-causing parasites can hitch a ride on microplastics and potentially spread throughout the seas.

Typically when people hear about plastic pollution, they might envision seabirds with bellies full of trash or sea turtles with plastic straws in their noses. However, plastic pollution poses another threat that’s invisible to the eye and has important consequences for both human and animal health.

Microplastics, tiny plastic particles present in many cosmetics, can form when larger materials, such as clothing or fishing nets, break down in water. Microplastics are now widespread in the ocean and have been found in fish and shellfish, including those that people eat.

As researchers studying how waterborne pathogens spread, we wanted to better understand what happens when microplastics and disease-causing pathogens end up in the same body of water. In our recent study published in the journal Scientific Reports, we found that pathogens from land can hitch a ride to the beach on microscopic pieces of plastic, providing a new way for germs to concentrate along coastlines and travel to the deep sea.

Investigating How Plastics and Pathogens Interact

We focused on three parasites that are common contaminants in marine water and seafoods: the single-celled protozoans Toxoplasma gondii (Toxo), Cryptosporidium (Crypto) and Giardia. These parasites end up in waterways when feces from infected animals, and sometimes people, contaminate the environment.

Crypto and Giardia cause gastrointestinal disease that can be deadly in young children and immunocompromised individuals. Toxo can cause lifelong infections in people, and can prove fatal for those with weak immune systems. Infection in pregnant women can also cause miscarriage or blindness and neurological disease in the baby. Toxo also infects a wide range of marine wildlife and kills endangered species, including southern sea otters, Hector’s dolphins and Hawaiian monk seals.

To test whether these parasites can stick onto plastic surfaces, we first placed microplastic beads and fibers in beakers of seawater in our lab for two weeks. This step was important to induce the formation of a biofilm – a sticky layer of bacteria and gellike substances that coats plastics when they enter fresh or marine waters. Researchers also call this sticky layer an eco-corona. We then added the parasites to the test bottles and counted how many became stuck on the microplastics or remained freely floating in the seawater over a seven-day period.

We found that significant numbers of parasites were clinging to the microplastic, and these numbers were increasing over time. So many parasites were binding to the sticky biofilms that, gram for gram, plastic had two to three times more parasites than did seawater.

Surprisingly, we found that microfibers (commonly from clothes and fishing nets) harbored a greater number of parasites than did microbeads (commonly found in cosmetics). This result is important, because microfibers are the most common type of microplastic found in marine waters, on coastal beaches and even in seafood.

Plastics Could Change Ocean Disease Transmission

Unlike other pathogens that are commonly found in seawater, the pathogens we focused on are derived from terrestrial animal and human hosts. Their presence in marine environments is entirely due to fecal waste contamination that ends up in the sea. Our study shows that microplastics could also serve as transport systems for these parasites.

These pathogens cannot replicate in the sea. Hitching a ride on plastics into marine environments, however, could fundamentally alter how these pathogens move around in marine waters. We believe that microplastics that float along the surface could potentially travel long distances, spreading pathogens far from their original sources on land and bringing them to regions they would not otherwise be able to reach.

On the other hand, plastics that sink will concentrate pathogens on the sea bottom, where filter-feeding animals like clams, mussels, oysters, abalone and other shellfish live. A sticky biofilm layer can camouflage synthetic plastics in seawater, and animals that typically eat dead organic material may unintentionally ingest them. Future experiments will test whether live oysters placed in tanks with and without plastics end up ingesting more pathogens.

The biofilms that form on microplastics can help pathogens spread through the sea. Emma Zhang, CC BY-NC-ND

A One Health problem

One Health is an approach to research, policy and veterinary and human medicine that emphasizes the close connection of animal, human and environmental health. While it may seem that plastic pollution affects only animals in the ocean, it can ultimately have consequences on human health.

Our project was conducted by a multidisciplinary team of experts, ranging from microplastics researchers and parasitologists to shellfish biologists and epidemiologists. This study highlights the importance of collaboration across human, animal and environmental disciplines to address a challenging problem affecting our shared marine environment.

Our hope is that better understanding how microplastics can move disease-causing pathogens in new ways will encourage others to think twice before reaching for that plastic straw or polyester T-shirt.

Republished with permission from The Conversation, by Karen Shapiro, Associate Professor of Pathology, Microbiology and Immunology, University of California, Davis and Emma Zhang, Veterinary researcher, University of California, Davis

The Conversation

The Conversation

The Conversation is a nonprofit, independent news organization dedicated to unlocking the knowledge of experts for the public good. We publish trustworthy and informative articles written by academic experts for the general public and edited by our team of journalists.

0 Comments

Submit a Comment

Your email address will not be published.

Related Articles

Jun 24 2022

The Need to Make Cities Ready for Climate Change

Efforts like reducing carbon emissions are important to fight climate change, but cities should also be looking at how they can reinforce roads, stabilize electric...
Jun 18 2022

Federal Court Rejects Trump EPA Glyphosate Decision Because Agency Ignored Cancer and Endangered Species Risks

The court’s ruling held the Trump administration’s 2020 interim registration of glyphosate to be unlawful because “EPA did not adequately consider...
Jun 14 2022

Summer in the City: Using Satellites to Help Combat the Urban Heat Island Effect

Industrial and commercial zones are frequently among the hottest areas, or heat islands, in cities. They typically have fewer trees to cool the air and more pavement...
windmills on green field under white sky during daytime
Jun 06 2022

A New Report Outlines Canada’s Rapid Path for Renewable Energy Transition

The transition would help Canada achieve its global climate commitments, create tens of thousands of new jobs and meet the growing demand for electricity.
May 22 2022

Australia’s Right-Wing Fossil Fuel Government Swept Aside in a Greenslide.

In an election largely fought on climate, Australia tosses the Prime Minister who once brought a lump of coal to parliament.
May 16 2022

Unfortunately Trees Are Not the Climate Change Cure-All We’ve Assumed They Would Be

Two studies show it is not a great idea to count on forests as a widespread carbon solution for climate change through the 21st century, particularly if societies don’t...
May 15 2022

Wealth Won’t Protect the Rich from Climate Change

Although wildfires in California have historically peaked in the late summer and fall, Orange County Fire Authority Assistant Chief of Field Operations TJ McGovern told...
May 06 2022

Fossil Fuel Democrats Join GOP Senators Trying to Prevent Biden From Declaring Climate Emergency

Though the Senate resolution is non-binding, it clearly shows the fear the fossil fuel industry has of impending actions to reverse the damage they are causing to our...
May 01 2022

Pumped Up Inflation: Big Oil Profits Double and Quadruple Amid Ukraine Crisis Excuses

One of the major factors of the current “inflation” is Big Oil intentionally profiteering off the war in Ukraine. Pump prices remain sky high even though no...
sunset
Apr 20 2022

Big Oil Loses Another Key Court Battle

A new court ruling is a major victory for California communities seeking their day in court against Big Oil polluters that spent decades lying about their...
Subscribe for Updates!

Subscribe for Updates!

Join our mailing list to receive the latest news and updates from our team.

You have Successfully Subscribed!

Pin It on Pinterest

Share This