More than 50 per cent of sea turtles are ingesting marine debris, a huge amount of which is floating around the world's oceans, scientists say.

Key points: 20 shopping bags (4-12 million tonnes) worth of debris entering the world's oceans from every metre of coastline annually

20 shopping bags (4-12 million tonnes) worth of debris entering the world's oceans from every metre of coastline annually South-East Asia found to be a major exporter of marine debris

South-East Asia found to be a major exporter of marine debris Turtles that eat fewer than 20 pieces will die from ingestion

On North Stradbroke Island, in Queensland's Moreton Bay, the turtle population has been affected by rubbish floating in the water and washing up on the shores.

The increasing presence of plastics ending up on even the world's most remote beaches by ocean currents has been taking a toll on the animals that inhabit the ocean and ingest the rubbish.

Dr Qamar Schuyler, a CSIRO scientist studying the impact of debris on local populations of marine animals, said somewhere between 4 and 12 million tonnes of debris were entering the world's oceans annually.

"If you broke that down to, say, every metre of coastline, there are about 20 shopping bags worth of debris that enters the ocean from every metre of coastline — so it's a huge problem," she said.

Dr Schuyler said they had done modelling using ocean current data to look at where the debris was coming from and had found that South-East Asia was a major exporter of marine debris — in particular China.

"But we also can't let that make us complacent," she said.

Dr Schuyler said they had found that in many areas of Australia the majority of debris produced ended up coming back to Australian shores.

"So we also need to look at our country and make sure our act is clean as well."

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She said that one of the ways they had been measuring the impact from marine debris, as well as measuring their success in dealing with it, was by using animals as a "bio indicator" and looking at those being affected.

"And we combined estimates of debris worldwide with where turtle populations are ... and we created a risk map, to see where in the world turtles are at highest risk of ingesting debris," Dr Schuyler said.

"We found that the coast of Queensland is one of the hotspots for marine debris ingestion for sea turtles."

How much debris does it take to kill a turtle?

Dr Schuyler said they took the predications they made globally and combined them with population estimates globally to try and establish how many turtles worldwide had ingested debris.

"And it's a tough thing because scientists deal with a lot of uncertainty, but if you pin me down and say, 'well, I need a number', we estimate that over 50 per cent of sea turtles around the world have ingested debris," she said.

"That's an enormous number ... of course I'm a scientist, so I have to give you caveat which is that we don't know yet how bad that number is.

"So we know that 50 per cent of turtles have eaten debris, but that doesn't necessarily mean that every single one of those turtles is going to die from eating debris."

To work that out, the team of scientists have been trying establish just how many pieces of debris it takes to kill a turtle.

"So we have found turtles out there that have been killed by long line fisheries and have over 100 pieces of debris in them — they weren't killed by the debris, they were killed by the fishery," she said.

"But then we find other turtles that have one piece of debris which was enough to kill them."

They were still working on the data, she said, but in terms of an early estimate "the likelihood is that 50 per cent of turtles that eat fewer than 20 pieces will die from ingestion".

Plastics are increasingly ending up on even the world's most remote beaches. ( Getty Images )



'Smalls things you can do to make a huge difference'

Dr Schuyler said while there needed to be more action from politicians globally, working together, local people could also be doing more to try and create change.

"A lot of this stuff is local government policies that can make a difference," she said.

"And people influence local government, so it's not an intractable issue, it's something that we can work on piece by piece."

She said that included "making sure that your local councils have adequate sewerage outfall management, that they have drains, [and] that the storm drains are fitted with ways of reducing the amount of plastic that flows into them".