Teenage turtles like Cliff are lucky to be rescued, because many are dying after eating hidden plastic pollution in Sydney Harbour and the Hawkesbury River when they come in summer to feed on seagrass meadows.

The Taronga Wildlife Hospital is treating a juvenile turtle dubbed Clifton, because it was found at Clifton Gardens on the north shore.

Hospital manager, Libby Hall, said snorkelers discovered the turtle on December 28. It could not swim or feed because it had ingested plastic.

“He was found covered in barnacles. He had barnacles all over his eyes. All over his shell,” Ms Hall said.

“He was in a very bad state. He was very, very thin and weak.”

Ms Hall said only one in 1000 green turtles survive to adulthood, and any death is significant.

It is believed Cliff is a teenage turtle, about 17 or 18 years old. Green Turtles need to reach the age of 30 before they can reproduce.

“About 80 per cent of the marine turtles that come to the hospital are affected by marine debris,” Ms Hall said.

“They feed on jellyfish. And plastic bags look exactly like jellyfish. So do balloons for that matter.”

Ms Hall emptied a jar of plastic that was removed from the intestine of a juvenile green turtle that died in Sydney.

It was a startling haul from a relatively small creature.

“These are the plastics … there’s balloons in there as well. Recycled and hard plastics and string,” she said.

“Of the 45 turtles that we get each year … the majority are affected by marine debris, either plastic or fishing line and hooks.”

Why don’t the supermarkets ban the plastic bag?

Conservationists are calling for NSW to ban single-use plastic bags, which are a small but significant proportion of the 10 tonnes of plastic waste that litters the harbour and its foreshores each year.

David Thomas is the founder of a community group called Eco Divers.

A self-styled “environmental ninja”, he has been scouring the waters off Manly, removing rubbish for more than 30 years.

“Seventy-five per cent of what goes in the water stays in the water,” he said.

“Only about 25 per cent floats … the bulk is still underwater.”

After a half-hour dive at the western end of Manly Cove, Mr Thomas filled a mesh bag with rubbish, including balloons that had bite marks from where marine life had tried to eat it.

“This nylon balloon string is impossible to break,” he said.

“So that ends up as entanglement or they swallow that and it gets tangled up in their digestive system. And basically they’re either going to die or if we’re lucky, get rescued.”

Mr Thomas said supermarkets should reintroduce paper bags.

“I’m calling Woolworths out – you could be the first,” he said.

“Why do we need to be government-driven? Why don’t we do it from the bottom up? There’s certainly a lot of people who don’t want plastic bags. And the environment?

“Well, we can’t pay that price any longer.”

The ABC contacted Coles and Woolworths for comment. Both companies said they comply with government and territory regulation.

Or should this be a national issue?

So far South Australia, the Northern Territory, Tasmania and the ACT have banned single-use plastic bags. Queensland will join them next year.

Ian Kiernan, the Chairman of Cleanup Australia, said a NSW ban would be a quick and effective way to reduce pollution around Sydney.

“It’s up to the government to institute that. They’re avoiding it,” he said.

“The environment is under incredible stress.

“It’s not the harbour’s fault. It’s what’s dropped on the land that washes into the harbour through the streams and stormwater system. That’s where the problem comes from.”

Roads and Maritime Services has crews working on Sydney waters for 12 hours a day, seven days a week to clean up the rubbish – which is particularly bad after heavy rain.

Environmental officer Graham Phillis said: “All the stormwater drains just back up full of rubbish and stuff.

“When it rains it just floods the whole harbour and then we’re just absolutely flat out.”

In a statement, the NSW Environment Minister’s office confirmed it was looking at a national approach to reduce the impact of plastic bags.

Meanwhile the turtle Cliff is slowly gaining weight and preparing to go home.

“He’s quite feisty believe it of not and he swims around the pool and he’s really improved a huge amount,” Ms Hall said.

The turtle’s rehabilitation pool is clear and clean.

Cliff’s carers are worried because they cannot guarantee he will be safe from plastic when he returns to the ocean.

-ABC