The scientists describe a soup of micro-particles similar to the so-called Great Pacific Garbage Patch, a phenomenon discovered a decade ago between Hawaii and California. Researchers say other ocean garbage patches are likely to exist around the globe.

"We found the great Atlantic garbage patch," said Anna Cummins, who collected plastic samples on a sailing voyage in February.

The debris is harmful for fish, sea mammals — and at the top of the food chain, potentially humans.

Since cleaning the oceans may not be possible, advocates say the key is to keep more plastic out of oceans by raising awareness and, wherever possible, challenging our throwaway culture that uses non-biodegradable materials as 'disposable products'.

"Our job now is to let people know that plastic ocean pollution is a global problem — it unfortunately is not confined to a single patch," Cummins said.