In the decades that our discarded plastic waste has been finding its way into the environment, much of it is broken down into tiny pieces too small for us to see. 

So, Dr Katsia Pabortsava, from the National Oceanography Centre in Southampton, led an expedition to find all that missing microplastic – particles, smaller than the diameter of a human hair – floating in the Atlantic.

On that expedition from the UK to the Falklands, Katsia used what's essentially a large ocean-going sieve with a very fine mesh to drag through the top 200 metres of the sea at different locations. That revealed that up to 21 million tonnes of microplastic is floating in those upper layers of the ocean.

The team only analyzed their samples for the three most commonly used packaging plastics. So, they say their estimate is actually likely to be conservative.

But what these tones of microscopic fragments show is that decades of plastic pollution has been washed from rivers or even blown on the wind into the ocean.