Wild blue mussels in South Australia are eating about three and a half pieces of microplastics – a much larger meal of unwanted waste than researchers initially expected, a study shows.
At every beach sampled by Flinders University researchers, microplastic fibres and fragments were found in either the water or the sand including at Ceduna, Coffin Bay, Port Lincoln, Whyalla, Robe and Adelaide.
It's the first time the presence of microplastics along South Australia's coastline has been measured.
Biodiversity and conservation expert Karen Burke da Silva said researchers were surprised to find as much pollution as they did.
"We thought that Coffin Bay would be one of the lowest as it's such a clean area and not a high industry area, but we found a lot of microplastics there – much of it fishing line," Professor Burke de Silva said.
Researchers found fibres came from people's clothing and fishing line, while fragments came from bigger chunks of plastic floating in the ocean.
They believe while the pieces are microscopic in size, microplastics could be taking a toll on the environment, marine life, and potentially humans.
"We eat mussels and a variety of other seafoods, whatever health effects the microplastics are having on the seafood then it'll have a run-on effect to humans," Professor Burke da Silva said.
She said there was a potential for microplastics to find their way into human food supplies sourced from South Australian waters.
"We know it causes inflammatory responses in mussels, it can affect their reproduction and digestive season.
Call for change
Professor Burke de Silva said it was important the study led to a change in local waste management.
"Each area needs to think about what specifically is being added to the ocean from their sites.
"We want to ensure that councils are looking into some industries that are adding microplastics to the water.
"We don't want it to get worse. We do know it's coming from South Australia — it's unlikely it's drifting in from other parts of the world."
Microplastics found in backyard soilShe also said the aquaculture industry might also need to assess where they were farming.
"I think it's also very important that we look at where mussels and other seafood is being farmed because if you want to avoid any kind of accumulation of microplastics then you want it in areas with low levels of pollution."
Microplastics were found to be more abundant in mussel samples near larger towns and cities, with levels four times higher at Semaphore Beach compared to the more remote Ceduna on Eyre Peninsula.
But Professor Burke da Silva said other sites tested, while not as high in microplastic samples, have greater ecological significance.
"Whyalla, for example, is a breeding ground of the great cuttlefish in the Northern Spencer Gulf and [there are] marine ecosystems more diverse than the Great Barrier Reef [that] live in the waters of Coffin Bay.
"So clean-up and prevention measures are long overdue."
Aquaculture industry still confident
Eyre Peninsula Seafoods chief executive Mark Andrews said any type of non-natural waste in water was a cause for concern, but farmed seafood, such as mussels, was monitored closely.
"These types of wastes accumulate over many years along the shoreline. This research paper has assessed mussels that are along the shoreline, only in intertidal water zones," he said.
"All mussel harvesting zones in Australia are kilometres from the shoreline, where the mussels are grown 2 metres below the surface and are harvested within 12 months.
"The pristine waters of South Australia are monitored and managed by PIRSA's Aquaculture and the South Australian Shellfish Quality Assurance Program."
Mr Andrews said there has never been any evidence of microplastics in farmed mussels.
He said the industry was finding ways to fight pollution.
"Each company is allocated kilometres of shoreline where four times a year we walk and collect all waste which is weighed and recorded."
