A new method has been developed that could help scientists identify the “lost 99 per cent” of microplastics in the world’s oceans.

Microplastics are fragments of plastic measuring less than 5 millimetres. They mainly arise from large plastic objects, which accumulate in the oceans and slowly break down into smaller pieces.

These tiny plastics are by far the most common type of marine pollution, but their size means most of them aren’t being taken into account when scientists attempt to analyse their prevalence.

One study estimated that 99 per cent of plastic in the ocean remains unaccounted for.

In pictures: Plastic pollution around the world Show all 10 1 /10 In pictures: Plastic pollution around the world In pictures: Plastic pollution around the world Plastic pollution Plastic trashes drifting on the sea surface in Marseille's islands In pictures: Plastic pollution around the world Plastic pollution The Bishnumati river running through Kathmandu in Nepal. The river is full of litter and raw sewage which is emptied into the river. The local people see the river as a rubbish collection service In pictures: Plastic pollution around the world Plastic pollution Garbage in the harbour of Tripoli, Libya In pictures: Plastic pollution around the world Plastic pollution Plastic and other undissolvable wastes float over the polluted Vrishabhavathi River, which a few years back use to supply drinking water to Bangalore 48 km to the north, in Kundanahalli village, Ramnagaram district, India In pictures: Plastic pollution around the world Plastic pollution Children collect plastic to be sold and recycled at a polluted river in suburban Manila In pictures: Plastic pollution around the world Plastic pollution Plastic bags and other rubbish are collected from the waters of Manila Bay during a campaign by environmental activists earlier this year Getty Images In pictures: Plastic pollution around the world Plastic pollution A man collects plastic bags and other rubbish from the waters of Manila Bay In pictures: Plastic pollution around the world Plastic pollution A woman throws out a doll while she selects recyclable plastic bottles, along Tiete river where floating foam blocks emit harmful gasses, in Pirapora de Bom Jesus, 60 Km north of Sao Paulo, Brazil In pictures: Plastic pollution around the world Plastic pollution Baby sea otter pup chews on a plastic cookie wrapper In pictures: Plastic pollution around the world Plastic pollution Bin overflowing with plastic rubbish, central London

Now, scientists have used a fluorescent dye that specifically binds to plastic in order to accurately count the very smallest plastic fragments.

They found many more microplastics than were previously estimated.

“Using this method, a huge series of samples can be viewed and analysed very quickly, to obtain large amounts of data on the quantities of small microplastics in seawater or, effectively, in any environmental sample,” said University of Warwick researcher Gabriel Erni-Cassola, lead author of the Environmental Science & Technology study.

Prior to this, methods to assess microplastic prevalence have relied on scientists picking them out of seawater samples one by one.

By adding their dye to samples, the scientists were able to easily detect fragments under a microscope in samples taken from the coast around Plymouth. This allows the process to be automated.

"Have we found the lost 99 per cent of missing plastic in surface oceans? Obviously this method needs to be implemented in future scientific surveys to confirm our preliminary findings,” said co-author Dr Joseph Christie-Oleza, also at the University of Warwick.

Many of particles they detected were no bigger than the width of a human hair, but even they can potentially be harmful to the environment, especially when ingested by animals.

In a recent episode of Blue Planet II, viewers saw the plight of a pilot whale calf that may have been a victim of plastic poisoning via contamination in its mother’s milk.

“Unless the flow of plastics and industrial pollution into the world's oceans is reduced, marine life will be poisoned by them for many centuries to come,” said Sir David Attenborough in his voiceover.

As it stands, scientists still have much to learn about the toxic effects of plastic. Microplastics are certainly eaten by many animal species at the expense of actual food, and this can lead to starvation.

It is also possible that chemicals and contaminants from the microplastics are absorbed by animals when they eat them, affecting their behaviour and bodily functions.

This makes attempts to measure the extent of the plastic problem vital.

"One of the major challenges right now is detecting the small stuff and extracting it from complex matrices," said Dr Chelsea Rochman, a plastic pollution researcher at the University of Toronto who was not involved in the study.

"I'd say I'm thrilled to see people working on this and that it seems this method may have some promise," said Dr Rochman.