A major study has revealed a shocking truth about what is lurking beneath the surface of Melbourne’s two most famous rivers.
The amount of plastic pollution flowing through Melbourne’s two most famous rivers has increased at an alarming rate, a three-year study has found.
The research – conducted by the Port Phillip EcoCentre between July 2017 and June 2020 – found more than 2.5 billion litter items flowed into Port Phillip Bay each year from the Yarra and Maribyrnong rivers.
More than two billion, or 85 per cent, of those items were microplastics, the Clean Bay Blueprint study revealed.
Microplastics are pieces of plastic smaller than 5mm in diameter, which originate from broken-up larger plastic products, and carry the potential to cause harm to aquatic life.
The study found the Yarra carried “significantly more litter” with 40,030 items removed from its surface waters during the research period compared to 13,658 from the Maribyrnong.
Litter in the Yarra increased by 400 per cent from 2016 to 2017 and doubled from 2018 to 2019.
The Maribyrnong saw a more gradual increase over time but still increased by about 57 per cent to 83 per cent year-on-year since 2017.
“An alarming result of this study is that litter is increasing in both the Maribyrnong and the Yarra, with plastic pollution in the Yarra increasing at a much faster rate,” the report said.
“In both rivers, the vast bulk of the litter caught consisted of hard plastic remnants of broken-up plastic items, followed by polystyrene and soft plastics.”
Polystyrene, which the report noted was likely to have come from building sites, was more likely to be found in the Yarra, while the Maribyrnong carried more nurdles, plastic bottle caps, plastic straws, twine and cigarette butts.
The study also found that plastic straws were the only litter item to decline over time, which it concluded was most likely due to community advocacy and action by retailers to reduce their use.
“This study demonstrates that Melbourne faces an alarming increase in waterway contamination,” it said.
“This poses particular concern considering the relatively enclosed configuration of Port Phillip Bay and the bay’s importance as a recreational fishery.”
The report also stated the every one of the researchers 113 trawl samples taken from the two rivers and analysed between January 2015 and February 2020 contained plastic pollution.
The study was funded by the Victorian Government’s Port Phillip Bay Fund, as part of their commitment to deliver the Port Phillip Bay Environmental Management Plan 2017–2027.
The Clean Bay Blueprint aims to quantify plastic pollution through microplastics trawls and beach litter audits to engage the community in citizen science activities and build partnerships with organisations to target litter and bay health.
The report made six recommendations – improve product stewardship, cultivate effective partnerships, support local councils in waste management, continue monitoring (micro) plastics pollution, increase education and plastic literacy and conduct further research.