TECH 6/30/2014 @ 5:44PM

The Mystery Of The Missing Ocean Trash

Deep in the ocean is a plastic vortex, the Great Pacific Garbage Patch.

Some people say it’s twice the size of Texas, others that it’s bigger than the continental United States. But the latest research indicates it doesn’t have nearly as much pollution as scientists thought it would.

And that’s worrying.

If our garbage is missing, we can’t keep tabs on what damage it is doing.

The US National Oceanic and Atmospheric Administration first predicted rubbish patches (there are several, three alone in the “horse latitudes” of the North Pacific) in 1988. Charles Moore, founder of the Algalita Marine Research Foundation in California, discovered the first one, the Eastern Garbage Patch, in 1997.

Like other patches it is formed of floating plastic and other debris that has been concentrated by the ocean’s circular currents, which act like conveyor belts.

You can’t see the debris from space, or the air, and it can easily be missed by an observer on the deck of a ship. The only sure way to spot it is to collect samples.

Plastic waste tends to accumulate in a few patches of each ocean (Credit: Kevin Krejci)

Which is exactly what Professor Andres Cozar from the University of Cadiz CDZI -1.42% and his colleagues did on the 2010 Malaspina Expedition, funded by the Spanish National Research Council. The Spanish ships RVHesperides and RV Sarmiento de Gamboa circumnavigated the globe, traveling 33,000 nautical miles (61,000km) and carrying 250 scientists. They collected over 3,000 samples from 141 sites, plus data from other sources.

Their results, published in the Proceedings of the National Academy of Sciences, were startling. They calculated that the oceans have between 7,000 and 35,000 tons of floating plastic.

Which is bad enough.

But they had expected to find 100 times that much, millions of tons, based on the rapidly growing production of the artificial polymers since the 1970s.

Plastic tends to break down into smaller pieces in the sea, so scientists were prepared to find many more small particles. But their nets hauled in far fewer pieces under 5mm (1/5in) than they should have.

Several ideas have been floated to explain what has happened to the missing garbage.

One is that the plastic is being drawn down into the depths of the ocean. Various marine plants and animals could be anchoring themselves to the debris – a process called biofouling – making it so heavy that it no longer floats.

“The deep ocean is a great unknown,” said Dr Cozar. “Sadly, the accumulation of plastic in the deep ocean would be modifying this mysterious ecosystem — the largest of the world — before we can know it.”

Another is that the tiny plastic particles are being eaten by small marine creatures, which are in turn eaten by larger fish which may ultimately end up in the human food chain.

“The plastic pollution in surface waters can more easily interact with the ocean life, because the surface layer of the ocean hosts most of the marine organisms,” Cozar said.

Another is that marine bacteria are breaking smaller pieces of plastic down to sub-microscopic sizes.

Finally, though the authors don’t give it much support, the smaller particles could be washing ashore.