Marine plastic is a breeding ground for disease-causing bacteria - Oceanographic
Ocean Plastics

Marine plastic is a breeding ground for disease-causing bacteria, study finds

Ocean Plastics

Marine plastic is a breeding ground for disease-causing bacteria, study finds

Plastic pollution is an ever-growing problem, leading to a significant amount of plastic waste accumulating in the environment, including the oceans. For the first time ever, a study now reveals that marine plastic particles also serve as platforms for bacterial community growth that are responsible for diseases in both humans and animals.

27/01/2025
Words by Nane Steinhoff
Photographs by Naja Bertolt Jensen

Microplastics – plastic particles under 5mm – are a widespread environmental pollutant. A recent study, conducted by the 5 Gyres Institute and published in the journal Plos One, took a closer look at plastic pollution trends between 1979 and 2019 and found that in 2005, around 16 trillion plastic particles floated in the oceans. Today, that number has increased to approximately 171 trillion pieces. 

But the amount of plastic particles entering the oceans is not the only concern. A new study, conducted by scientists at Plymouth Marine Laboratory and the University of Exeter, has now revealed that the particle type also affects the colonisation, enrichment and spread of both antimicrobial-resistant (AMR) and pathogenic (disease-causing) bacteria.

It’s nothing new that upon entering the environment, microplastics are rapidly colonised by diverse microbial communities, forming what is known as the ‘plastisphere’, a human-made ecosystem of microorganisms such as bacteria, algae, and other single-celled organisms. 

But, owing to the frequent omission of other appropriate materials, such as natural substrates, with which to compare in previous studies, there was a lack of scientific evidence supporting the unique risks posed by microplastics through the enrichment and spread of AMR pathogens. 

The new study investigated selective colonisation by a sewage community on environmentally sampled microplastics, involving three different polymers, sources and morphologies, alongside a natural substrate (wood), inert substrate (glass) and free-living/planktonic community controls.

This study showed that marine plastic substrates served as a platform for the selective growth of bacterial communities responsible for diseases in both humans and animals. Compared to controls, polystyrene and wood were selectively colonised by AMR bacteria, and bio-beads enriched strains of Escherichia coli, which can cause diarrheal illnesses. It further found that surface weathering of the plastic particles did not significantly influence AMR colonisation. 

Lead author of the study, Emily Stevenson, who is a PhD student with Plymouth Marine Laboratory and the University of Exeter, commented: “By identifying particles of greater concern for AMR risk, we can recommend improvements to waste management or sewage treatment, with the aim to reduce emissions of these materials into the environment.

“We would like to see policy recommendations that include proposed improvements to environmental monitoring of both microplastics and antimicrobial micropollutants. We also suggest that efforts to reduce the spill of bio-beads should be prioritised considering their effect on E. coli communities.”

Interestingly, under ‘normal’ circumstances, the community composition is largely driven by the external community and environment. Yet in this study all particles were exposed to the same environment, suggesting that the selective colonisation observed is a result of substrate-specific drivers.

Furthermore, given that there was no difference in the size of the particles used in this study, this suggests that there are specific differences in particle characteristics that affected the attachment of AMR or pathogenic bacteria.

There are also reasons to suggest that the attachment of bacteria to plastics may make them more likely to become resistant to antimicrobial treatment, such as the dynamics of the microbial community that attaches to the material and previous exposure to plastic-associated chemicals. However, further research is required to fully understand whether plastics, specifically microplastics, pose a greater risk than natural debris in supporting these disease-causing or drug-resistant microbial communities.

Read the full study here

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Words by Nane Steinhoff
Photographs by Naja Bertolt Jensen

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