Microplastics found by Flinders University in South Australia coast mussels: not in farmed mussels, says industry
The South Australian seafood industry said there was no evidence of microplastics in farmed mussels that grew under different conditions from those studied by Flinders University in intertidal shoreline zones.
Image courtesy Flinders University
Microplastics were found in wild blue mussels around the South Australian coast in the first sampling by Flinders University researchers.
In a 2022 report on the study, the Flinders researchers found that mussels were eating about three and a half pieces of microplastics – a much larger amount than they expected. At beaches including Ceduna, Coffin Bay, Port Lincoln, Whyalla, Robe and Adelaide, microplastic fibres and fragments were found in either the water or the sand.
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 biodiversity and conservation expert professor Karen Burke da Silva said sites such as Coffin Bay, while not as high in microplastic samples, had 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”.
Burke da Silva said researchers thought Coffin Bay would be one of the lowest and not a high-industry area “but we found a lot of microplastics there – much of it fishing line." Researchers found fibres came from people's clothing and fishing line with fragments from bigger pieces of plastic in the ocean. They believed, while the pieces were microscopic, the plastics could be taking a toll on the environment and marine life. There was potential for microplastics to find their way into human food sourced from South Australian waters.
Burke da Silva said: "We know it (plastic) causes inflammatory responses in mussels. It can affect their reproduction and digestive season. If these marine organisms are having a negative health reaction to microplastics then humans presumably will too."
Eyre Peninsula Seafoods chief executive Mark Andrews said there had never been any evidence of microplastics in farmed mussels. Non-natural waste in water was concerning but farmed seafood, such as mussels, was monitored closely: “This research paper has assessed mussels that are along the shoreline, only in intertidal water zones. These particular mussels would have been there for 20 years or more. The growth in any intertidal zone is 100% slower than in a subtidal zone where all farmed mussels in Australia are grown. All mussel harvesting zones in Australia are kilometres from the shoreline, where the mussels are grown two metres below the surface and are harvested within 12 months.”
The waters of South Australia were monitored and managed by the state government’s primary industries and regions (PIRSA) aquaculture and the South Australian shellfish quality assurance programme.
Andrews 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."
