Eating plastic makes for smaller mussels

Microplastics are stunting the growth of mussels in Victoria’s Port Phillip Bay, according to a study by RMIT marine ecologists.

Study lead author Dr Charlene Trestrail said mussels ingest microscopic pieces of plastic used in cosmetics, affecting their ability to grow and reproduce.

The microplastics travel from our bathroom sinks to the ocean, where they are easily confused with algae or seaweeds.

Because mussels cannot tell the difference, they take in the plastic along with their normal diet of algae.

Trials on mussels collected from Newport, Victoria were conducted in water of varying microplastic levels.

Trestrail said the plastics affected the action of four of the invertebrates’ key digestive enzymes, which means they struggle to break down starch into the simple sugars they need to survive.

“We don’t think the plastic affects mussels directly, but it does reduce their ability to digest the real food in their gut, which means they miss out on energy and nutrients,” Trestrail, who conducted the work with RMIT’s Ecotoxicology Research group, said.

If they can’t digest food effectively, the mussels can struggle to grow, so they end up smaller overall.

Trestrail said mussels also need energy to mate and reproduce, which could have serious ramifications for biodiversity in the bay.

“Besides being a tasty treat for humans, mussels play an important role in keeping marine ecosystems healthy,” Trestrail said.

“Because plastic can affect their ability to breed, we could see a drop in mussel populations in Port Phillip Bay, with knock-on effects for other marine wildlife.”

Photo of microplastics in mussel stomach.

Mussels in Port Phillip Bay near Melbourne are ingesting microscopic pieces of plastic used in cosmetics.

Environmental campaigners have worked hard to reduce the amount of plastic in the oceans from easily visible things like shopping bags and packaging.

But Trestrail said it’s time to highlight the lesser-known impact of microbeads and other hidden plastics in products like toothpaste and bath scrubs.

Her study, which she published last year as part of her PhD at RMIT University, was one of the first to investigate how tiny plastics affect a common marine mussels’ digestion.

“We know lots about how plastics affect animals externally – we've all seen photos of birds and turtles entangled in plastic – but now we know more about what plastics do internally,” Trestrail said.

“We found tiny pieces of plastic had a big impact in mussels’ digestion, hampering their ability to get energy out of their food.”

There has been a push in recent years for new legislation to reduce microplastic pollution, from microbeads in bathroom products to fibres in synthetic fabrics.

Dr Charlene Trestrail conducted her work with RMIT’s Ecotoxicology Research group.

Previous research by Trestrail and RMIT’s Ecotoxicology Research group showed the plastic water-absorbing green floral foam used by florists can be ingested by a range of freshwater and marine animals.

But while the federal government has supported the cosmetics industry to start phasing out microbeads, the 2021 National Plastics Plan stopped short of banning or regulating their use.

Trestrail said we need to take pollution from microplastics and microbeads more seriously.

“Because they’re so small, once they’re in the ecosystem they are almost impossible to remove. The only solution is not to use them in the first place,” she said.

Trestrail has completed her PhD and is keen to continue her important ecotoxicology research.

‘Microplastics alter digestive enzyme activities in the marine bivalve, Mytilus galloprovincialis’, with co-authors Charlene Trestrail, Milanga Walpitagama, Ana Miranda, Dayanthi Nugegodaa and Jeff Shimeta, is published in Science of the Total Environment (DOI: 10.1016/j.scitotenv.2021.146418).

Trestrail’s research has been featured by Science in Public as part of Fresh Science, a program helping early career researchers share their stories of discovery with the world.

Story: Tamzin Byrne, Aeden Ratcliffe

Science

28 March 2022

Return to RMIT News

Science

28 March 2022

Research
Environment
Science and technology
Sustainability

Engage

Contact RMIT News

Find an expert

Study with us

Research at RMIT

Related News

Cairns Airport mangrove study sets new standard for Indigenous-led research on country

A new study highlights how Indigenous leadership, science and business can unite to protect coastal ecosystems while building long-term environmental and cultural knowledge.

Bird's eye view of the coffee concrete footpath being laid along a busy road in Pakenham. Credit: Pete Glenane, HiVis Pictures

Coffee waste helps make lower carbon concrete

RMIT researchers are advancing new ways to cut the carbon footprint of infrastructure by turning everyday organic waste into useful construction materials.

RMIT student wins Best in Category at Victorian Premier’s Design Awards

A sustainable furniture system using digital fabrication techniques and repurposed furniture waste has won Best in Category for Student Design at the Victorian Premier’s Design Awards alongside over twenty RMIT-affiliated projects recognised at this year’s awards.

gelthumbnail-aus-antarctic-fellowship-25-1220x732px.jpg

RMIT academic announced as 2025 Australian Antarctic Arts Fellow

RMIT Media & Communications Lecturer, artist and filmmaker Dr Polly Stanton has been announced as the 2025 Australian Antarctic Arts Fellow.

Acknowledgement of Country

RMIT University acknowledges the people of the Woi wurrung and Boon wurrung language groups of the eastern Kulin Nation on whose unceded lands we conduct the business of the University. RMIT University respectfully acknowledges their Ancestors and Elders, past and present. RMIT also acknowledges the Traditional Custodians and their Ancestors of the lands and waters across Australia where we conduct our business - Artwork 'Sentient' by Hollie Johnson, Gunaikurnai and Monero Ngarigo.

More information

Eating plastic makes for smaller mussels