Nearly 269,000 tons of plastic pollution may be floating in the world's oceans, a study said Wednesday.

Plastic pollution is ubiquitous throughout the oceans, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere and remote regions.

To better estimate the total number of plastic particles and their weight floating in the world's oceans, Marcus Eriksen from the Five Gyres Institute in the U.S. and colleagues used data from 24 expeditions collected over a six-year period between 2007 and 2013 across all five sub-tropical gyres, coastal Australia, Bay of Bengal, and the Mediterranean Sea.

The data included information about microplastics collected using nets and large plastic debris from visual surveys, which were then used to calibrate an ocean model of plastic distribution.

"This is the first study that compares all sizes of floating plastic in the world's oceans from the largest items to small microplastics," said the study in the open-access journal PLOS ONE.

"Based on our model results, we estimate that at least 5.25 trillion plastic particles weighing 268,940 tons are currently floating at sea."

Large plastics appear to be abundant near coastlines, degrading into microplastics in the five subtropical gyres, and that the smallest microplastics were present in more remote regions, such as the subpolar gyres, it said.

The distribution of the smallest microplastics in remote regions of the ocean may suggest that gyres act as "shredders" of large plastic items into microplastics, after which they eject them across the ocean, said the study.

"Our findings show that the garbage patches in the middle of the five subtropical gyres are not the final resting places for the world's floating plastic trash," Eriksen said in a statement.

"The endgame for micro-plastic is interactions with entire ocean ecosystems."

The researchers also stressed that their estimates are highly conservative, and may be considered minimum estimates.

The study did not account for the potentially massive amount of plastic present on shorelines, on the seabed, suspended in the water column, and within organisms.

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