Plastic detectives: science meets stewardship
- Jul 2
- 5 min read
The Australian Institute of Marine Science deciphers microplastics evidence to support mitigation and reduce impacts.
Our creeks, rivers, and coastlines are central to life in Townsville - places we fish, swim and connect with nature. Over two-thirds of locals consider litter and marine debris to be a big problem for our waterways.* Whilst plastic bottles and wrappers are easy to spot, what about the pollution we can’t see?
Microplastics. These tiny fragments, which are smaller than five millimetres, are becoming one of the biggest unseen threats to our waterways. They come from everyday things: clothing fibres shed in the wash, microbeads in foundation, and large plastic items that have broken down into smaller and smaller pieces. Too small to be caught by standard filtration systems, they slip into waterways, where they’re easily eaten by marine life and can even move up the food chain.
Microscopic doesn’t mean harmless, just harder to track.
As part of their long‑standing commitment to protect Australia’s marine environments, the Australian Institute of Marine Science (AIMS), one of our key research partners, are on the front line of microplastics research and monitoring. They’re working to uncover how widespread these particles are in the ocean and what they mean for the health of marine ecosystems.
Tracking microplastics across the Reef
How do you investigate something you can’t see with the naked eye, especially when it floats, sinks, and drifts with the currents?
AIMS scientists start with a specialised tow that skims the ocean surface, collecting seawater samples along with any floating microplastics.
But plastics don’t always float. As fragments gather “passengers” like algae or barnacles, they grow heavier and begin to sink. Some polymer types are naturally denser and drift downward more rapidly.
AIMS microplastic scientist, Dr Cherie Motti says the team are pioneering techniques to extend the depth at which sampling occurs.
“By sampling further below the surface, scientists can better understand the amount of microplastics in the ocean.”
The deeper they look, the more evidence they uncover.
Deciphering microplastic evidence
Back on shore, each sample becomes a mini-investigation. Scientists look for clues in:
Shape and form. Fragments, fibres, beads or nurdles all provide clues about their origin.
Polymer type. Chemical analysis reveals the plastic’s “polymer fingerprint,” such as polypropylene (PP), polyethylene (PE), or nylon.
Concentration levels. Particle counts show the scale of pollution, and how levels shift over time and across locations.
“Together, these measurements not only reveal how much plastic is in the marine environment, but improve our understanding of microplastic contamination, its sources, and its effect on marine life and ecosystems, to aid mitigation efforts across the Great Barrier Reef,” says Dr Motti.
Every particle is a clue, and every clue adds to the bigger picture.
What the clues reveal
Since AIMS began monitoring microplastics, concentrations across the region have remained relatively stable. But after major weather events, the story changes.
Following the 2019 Townsville floods, scientists recorded a significant spike in plastics. Extreme rainfall and runoff sweep land-based waste from rivers and creeks straight into the ocean.
Moments like this reveal just how connected our catchments and coastlines are, and why stewardship on land is important.
Through the Marine Monitoring Program, AIMS conducts microplastics surveys at seven inshore locations along the Great Barrier Reef three times each year. Their work also extends nationally, with ten additional monitoring sites included in the Integrated Marine Observing System (IMOS).
Small particles, big picture
To find these microscopic bits of evidence, a team of detectives work together. Across the country, AIMS leads the IMOS Marine Microplastics sub‑facility, with Dr Cherie Motti heading a national team of collaborators from CSIRO, SARDI, NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW) and Deakin University.
Together, they collect clues from coastal waters nationwide, pooling their findings into annual report cards. These reports help reveal long‑term trends, pinpoint hotspots, and show how microplastic types and characteristics shift from year to year.
Dr Motti says, these insights don’t just advance science, they inform both local and national efforts to manage plastic pollution and protect Australia’s marine ecosystems.
Choosing better plastics (or none at all)
Although the Great Barrier Reef doesn’t experience the extremely high microplastic concentrations recorded elsewhere in the world, they remain a consistent and concerning presence.
“They’re found on every monitoring trip,” says Dr Motti.
Marine life can accidentally consume these tiny particles, which stays in their stomachs. This can cause an additional problem, as harmful chemical additives added to plastics to give them specific properties, such as colour or flexibility, can leach into body tissues.
“AIMS research has shown that animals often contain more microplastics than what’s found in the surrounding environment,” says Dr Motti.
At sampling sites, the most common polymer types detected are polypropylene (PP) and polyethylene (PE). These plastics are widely used in everyday items such as food packaging, takeaway containers, bottle lids, synthetic ropes, and disposable products. PP fibres are also commonly shed from outdoor gear and activewear.
What can you do? Small choices make a meaningful difference:
Choose plastic‑free alternatives such as shampoo bars, bar soaps, or refillable household products.
Opt for natural fibres, such as cotton, wool, hemp, or bamboo, over synthetic fabrics that shed PP or PE fibres.
Reduce single‑use items wherever possible by choosing reusable, durable products.
During the wet season, be especially mindful of waste: heavy rainfall and runoff can quickly carry plastics into waterways and out to sea, including debris long trapped in vegetation along riverbeds.
Microplastics in the Townsville and Dry Tropics Waterways Report Card
At present, the Waterways Report Card measures litter and marine debris pressure, helping to track what’s visible on our beaches, creek banks, and shorelines.
But the vision extends further.
There is strong hope that future Report Cards will include a dedicated measure for microplastic pollution. This will help raise awareness of these tiny invaders and build a more complete picture of plastics in our environment, from the rubbish we can pick up to the particles we can’t see.
The Healthy Waters Partnership Senior Environmental Data Analyst, Dinny Taylor, explains:
“Our community is telling us that they see litter and marine debris to be a big problem to our waterways, so we are working with our Partners to bring a more complete picture of these impacts together in the Waterways Report Card, helping to tell the story that litter is a source for microplastics and marine debris in our rivers, creeks, and coasts.”
*Source: 2024 SELTMP survey results for the Dry Tropics
