National & World News

New study finds plastic accumulation in food may be underestimated

26-Jul-2021 9:00 AM EDT, by University of Portsmouth

Newswise — A new study has found plastic accumulation in foods may be underestimated. There is

also concern these microplastics will carry potentially harmful bacteria such as E. coli, which are

commonly found in coastal waters, up the food chain.

Researchers from the University of Portsmouth tested a theory that microplastics covered in a biofilm

coating (much like natural algae) were more likely to be ingested by oysters than microplastics that

were completely clean. Although the experiment was carried out on oysters under laboratory

conditions, scientists believe similar results could be found in other edible marine species that also filter

seawater for food.

Up until now, studies to test the impacts of microplastics on marine life have typically used clean, virgin

microplastics. However, this is not representative of what happens to microplastics in the marine

environment. Bacteria readily colonise microplastics that enter the ocean. In this study, published in

Science of the Total Environment, scientists compared the uptake rates of clean microplastics versus

microplastics with an E.coli biofilm coating. The results were worrying - oysters contained 10 times

more microplastics when exposed to the biofilm coated beads. It is hypothesised that these coated

MPs appeared to be more like food to the oysters, explaining their preferential ingestion over clean


The scientists say the implications for the food chain are concerning. The ingestion of microplastics is

not only bad for the oysters, but it affects human health too. The plastic does not break down in the

marine animal and is consumed when we eat it.

Lead researcher, Dr Joanne Preston, Reader in Marine Ecology and Evolution at the University of

Portsmouth, said: “What we’ve discovered is that microplastic really is the Trojan Horse of the marine

world. We discovered that clean plastics had little impact on the oysters’ respiration and feeding rates -

but did have an impact when you fed them the microplastic hidden in the biofilm. The oysters took in

more and it affected their health. It is unsure exactly how much this could affect the food chain, but the

likelihood is because the creatures are ingesting more plastic and potentially, disease causing

organisms, this will ultimately have a negative effect on human health. We know microplastics can be

the mechanism by which bacteria are concentrated in coastal waters and this shows that they are more

readily taken up by shellfish, and can be transferred to humans or other marine life.”

Dr Preston said: “We have successfully tested a hypothesis – this opens the door for more research on

environmentally relevant studies of the long term impacts of biofilm coated microplastics on a wider

range of marine life. We also need to study the transfer of microbes up the food chain via plastics in

much greater detail.”

Professor Steve Fletcher, Director of the University’s Revolution Plastics initiative, said: "The findings

in this research give us further insight into the potential harm microplastics are having on the food

chain. It demonstrates how we could be vastly underestimating the effect that microplastics currently

have. It is clear that further study is urgently needed.