Over five trillion pieces of plastic floating in world oceans: Study

WASHINGTON: More than five trillion pieces of plastic - collectively weighing nearly 270,000 tonnes - are floating in the world's oceans, including the Indian Ocean, a new study has found.

Microplastic pollution is found in varying concentrations throughout the oceans, but estimates of the global abundance and weight of floating plastics, both micro and macroplastic, lack sufficient data to support them, researchers said.

To better estimate the total number of plastic particles and their weight floating in the world's oceans, scientists from six countries contributed data from 24 expeditions collected over a six-year period from 2007-2013 across all five sub-tropical gyres, coastal Australia, Bay of Bengal, and the Mediterranean Sea.

A gyre in oceanography is any large system of rotating ocean currents, particularly those involved with large wind movements.

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.

Based on the data and model, the authors of the study estimate a minimum of 5.25 trillion plastic particles weighing nearly 269,000 tonnes in the world's oceans, researchers said.

Large plastics appear to be abundant near coastlines, degrading into microplastics in the 5 subtropical gyres, and that the smallest microplastics were present in more remote regions, such as the sub-polar gyres, which the authors did not expect.

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, researchers said.

"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," said Marcus Eriksen, Director of Research for the 5 Gyres Institute in Santa Monica, California US.

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

The study was published in the journal PLOS ONE.