Microplastic particles polluting our oceans and harming sealife have now been found off Antarctica - some of the most pristine and unspoilt waters on the planet.

The alarming finding, announced by scientists who reviewed samples collected in the Volvo Ocean Race, comes as New Zealand researchers have begun a new study looking at how other materials break down in the water.

Microplastics are small particles of plastic, often invisible to the naked eye and measuring less than 5mm.

Still, they pose a grave threat to the planet's oceans, where they can enter the food chain in species like tuna and mackerel, and potentially later cause harm to us.

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It's estimated an annual eight million tonnes of plastics enter oceans, where they eventually break down into microplastics.

The problem - worsened by a 20-fold increase in plastic production over the past 50 years - could mean, by 2050, the volume of plastic in oceans outweighs that of even fish.

In some places, microplastics already outnumbered plankton by six to one.

Plastic was now being found in rainwater, sea salt, and even air.

Nonetheless, scientists who analysed samples gathered by the Turn the Tide on Plastic race team were concerned to find microplastics in the Southern Ocean, close to the Antarctic Ice Exclusion Zone.

The waters around the frozen continent are considered some of the cleanest in the world, offering scientists a crucial control with which to study oceans, and prompting nations to increase protection through new reserves, including a 1.1 million sq km marine protected area that now spans much of the Ross Sea.

Dr Soren Gutekunst, a scientist at German ocean research institute GEOMAR, said the samples collected during the global race was "extremely valuable".

"This new information confirms the results we had previously collected from European waters and shows that there are consistently high levels of microplastic in the ocean and we are also seeing low levels of microplastics in waters close to the Antarctic."

Compared to other oceans the number of microplastic particles was small, measuring at four microplastic particles per cubic metre.

In Australian waters, close to Melbourne, one million microplastic particles per square kilometre of ocean were found.

Over one million microplastic particles per square kilometre of ocean were found in the Southern Atlantic Ocean, west of Cape Town, South Africa and on the third leg of the race, one and a half million microplastic particles per square kilometre of ocean were discovered east of South Africa.

Volvo's New Zealand general manager Coby Duggan says the new data will help inform scientists around the world.

"Little is known about the levels of microplastic pollution in our oceans but already this data is helping the scientific community around the world."

New Zealand has moved to ban microbeads, but the wider problem of microplastics couldn't be tackled in the same way.

The waters around the frozen continent are considered some of the cleanest in the world. Photo / John Weller
The waters around the frozen continent are considered some of the cleanest in the world. Photo / John Weller

Current legislation encouraged product stewardship and environmental responsibility at the beginning of a product's life cycle.

Microfibres go under the lens

Meanwhile, a new study being led by New Zealand scientists aims to shed light on similarly small microfibres, which can also enter oceans in large quantities.

Much of this could happen when tiny fibres were shaken loose from clothing and other
materials in washing machines, before travelling out to sea through drains.

In the ocean, smaller microfibres could be ingested by the marine life and can end up in our seafood, potentially creating health issues as volumes increase.

AgResearch senior scientist Steve Ranford said the limited data available suggests wool - being a natural protein fibre – broke down at a far greater rate in sea water, and therefore presented far less risk to the marine environment than synthetic fibres like polyester and nylon.

"To test that, we will be working with another Crown Research Institute, Scion, in an experiment that tests how samples from both woollen clothing and carpets biodegrade in controlled salt water conditions, compared to samples from the synthetic alternatives," Ranford said.

"This initial study will take place over a 90-day period, and from that our scientists will analyse the results and document what is left of the samples, and will be able to provide some information about how these materials break down and at what rate."

From there, the research would consider other factors relating to the different materials and how they broke down.

"The aim is provide the public with objective information as they make choices about what they buy, as well as inform manufacturers and retailers of the performance of goods like clothing and carpet," Ranford said.

"There is a growing movement around the world by industry and governments towards more transparency about products and their potential impacts on the environment, and having good quality research is important for this discussion."