What’s Happening?
Research from the Queensland Alliance for Environmental Health Sciences (QAEHS) and the University of Queensland (UQ) has unveiled the alarming accumulation of microplastics in Brisbane’s Moreton Bay, a shallow coastal bay shielded by Moreton and North Stradbroke Islands.
Led by QAEHS researchers Prof Kevin Thomas, Dr Elvis Okoffo, and Dr Ben Tscharke, alongside UQ’s A/Prof Helen Bostock and Dr Alistair Grinham, the study reveals that Moreton Bay now holds an estimated 7,000 tonnes of microplastic particles — equivalent to 700 million half-litre plastic bottles — that have flowed in through urban rivers, predominantly the Brisbane River.
Why it Matters
Plastic waste and its breakdown into microplastics (under 5mm) and nanoplastics (1 micrometre or less) are accumulating in marine ecosystems and embedding in seafloor sediments, especially in enclosed bays like Moreton.
These tiny pollutants are mistaken for food by marine life, impacting everything from microorganisms to larger animals, such as dolphins and seabirds. “Our analysis shows a direct link between microplastic concentration and population growth in Southeast Queensland,” the researchers stated, emphasising the scope of human influence on this issue.
By the Numbers
- Estimated Microplastics in Moreton Bay: ~7,000 tonnes
- Plastic Types Identified: Seven types, with polyethylene (PE) being the most common
- Microplastics Timeline: None were recorded before the 1970s, but concentrations increased exponentially post-2000, mirroring global plastic production trends.
Zoom In
The Moreton Bay ecosystem, including mangroves, seagrass meadows, and mudflats, shows diverse concentrations of microplastics in sediment.
Mangroves, in particular, are “very good at trapping sediment – and plastic,” the researchers highlighted, noting that PE, a primary material in single-use items like bags and chip packets, was the most abundant plastic type found.
Measuring Microplastics: Challenges and New Techniques
The research team, including Dr Okoffo, Prof Thomas, Dr Tscharke, A/Prof Bostock, and Dr Grinham, faced significant challenges in accurately measuring microplastics, which typically require laborious methods such as microscope observations and absorption spectroscopy.
However, the team applied a newer, more advanced technique — pyrolysis-gas chromatography mass spectrometry — that dissolves sediment samples and vaporises the plastic, allowing for accurate concentration measurements.
This method enabled the team to capture plastic particles smaller than 20 micrometres, which traditional methods often overlook. “Working out the volume of microplastics in an embayment like Moreton Bay presents unique challenges, but these measurements are vital to understanding the full extent of plastic pollution,” said the research team.
Zoom Out
Globally, similar cities with bays and estuaries may also be facing high microplastic accumulations, though the research in places like Melbourne’s Port Phillip Bay and Sydney Harbour remains pending. Moreton Bay’s study sheds light on the widespread risk posed by urban runoff.
Local Impact
For Redland, the proximity to Moreton Bay makes this finding especially significant.
The region’s coastal areas, including Cleveland and Victoria Point, interact closely with the bay’s habitats.
Redland’s economy, boosted by eco-tourism and recreational fishing, depends on a healthy bay environment, making microplastic pollution a direct concern.
The bay’s accumulating plastic threatens marine life and water quality, which could, in turn, impact Redland’s local industries and the natural environment Redland residents enjoy.
Addressing this issue could benefit not just Moreton Bay, but also the entire Redland community.
What to Look for Next
To confront this issue, it’s essential to implement better waste management policies and strategies aimed at reducing plastic consumption.
“Doing nothing means microplastics will keep building up, and up, and up,” the research team cautions, pointing to the urgency of policy intervention for the well-being of marine ecosystems.
Regional collaboration between communities like Redland, Brisbane, and other areas feeding into Moreton Bay will be key in creating meaningful change and safeguarding both marine biodiversity and economic activities tied to a healthy bay.
