The EcoCentre has been analysing tens of thousands of litter items gathered in the collections from both waterways. Hard plastics were the most common items found in both rivers, followed by polystyrene in the Yarra and soft plastics in the Maribyrnong River. Summer was the peak litter season for the Maribyrnong whereas it was both summer and winter for the Yarra. The estimated quantity of rubbish has increased markedly since The Age reported the first release of statistics from the research a year ago, which showed more than 800 million pieces of trash were flowing into Port Phillip Bay from the two rivers.

Port Phillip EcoCentre marine biologist Fam Charko said protecting the bay was a responsibility shared by all Victorians. “Port Phillip Bay is not like the ocean. It's a fairly enclosed marine ecosystem in the sense that it doesn't get plastic pollution from Asia or anywhere else in the world,” she said. The litter we find on bay beaches is ours and ours alone. It got there from the suburbs. Marine biologist Fam Charko “The litter we find on bay beaches is ours and ours alone. It got there from the suburbs, via the waterways and is not likely to float away elsewhere on the next tide.” But she was encouraged that the figures showed a reduction in the number of straws in the Yarra River, which was the only litter category to decline.

“That’s a nice surprise,” she said. “The community and businesses have been working really hard all over Victoria to reduce plastic straws.” Plastic straws are among the most common items found washed up on beaches around the world, according to Sustainability Victoria. A litter trap in the Yarra River near Webb Bridge. Credit:Eddie Jim But consumers and businesses have embraced alternatives to plastic straws, including glass, metal and paper. The EcoCentre conducted monthly top water trawls lasting 30 minutes in locations close to the bay, analysing more than 20,000 pieces of litter in total.

The EcoCentre’s Clean Bay Blueprint research project received funding from the Victorian government’s Port Phillip Bay Fund and the statistics were overseen by academics from Monash University. The EcoCentre hopes its study will lead to strong action as the Andrews government prepares a new marine policy and a plan for a “circular economy” designed to reduce waste and better use natural resources. Port Phillip EcoCentre executive officer April Seymore called for a “radical rethink” in the way we use plastics. She said everyone played a role in reducing plastic use, from product designers to politicians. “Let’s make the story we see with straws the story of all plastic products,” she said.

Mornington Peninsula anti-litter campaigner Josie Jones says a local push to eradicate plastic straws had been paying off. But Ms Jones, who is a keen underwater photographer, said she often saw the devastating effect of rubbish on local wildlife. She recently found a penguin on Dromana beach tangled in balloons. And plastic bags were potentially deadly for local seahorses, she said. “One plastic bag in a marine environment can suffocate a whole colony,” she said.

The Andrews government has moved to ban single-use plastic bags in shops and supermarkets across Victoria. The ban covers all light-weight single-use carry bags, including those made from degradable, biodegradable and compostable plastics. However, plastic bin liners, small clear plastic bags used for fresh fruit and vegetables and animal waste bags will be exempt from the ban. A spokeswoman for the Victorian government said it was working to protect the “treasured” Port Phillip Bay through a dedicated fund and management plan. “Port Phillip Bay is one of Victoria’s most precious natural assets and we’re partnering with community organisations to improve its health,” she said.

Monash University biological sciences and biostatisticslecturer Christopher Johnstone said plastics were particularly harmful for marine life, with animals often mistaking litter for food. “Animals don’t recognise that it’s something indigestible,” he said. Loading Replay Replay video Play video Play video Dr Johnstone, who oversaw the study’s statistics, said animals around the world were being found with stomachs full of plastic. In June last year a whale washed up in distress on a beach in Williamstown. The whale, which was pregnant, was later found to have a stomach full of plastic bags.

The animal’s death prompted calls from the Department of Environment and Zoos Victoria for people to dispose of their rubbish properly.