Debris like this washes up on Antarctic shorelines
(Image: British Antarctic Survey)
(Image: British Antarctic Survey)
David Barnes of the British Antarctic Survey says floating plastic provides a vehicle for marine organisms like barnacles, worms and molluscs to travel much further than they would normally.
His study, published in the journal Nature, says many species seem to prefer man-made rubbish to natural debris like volcanic rock, pumice and wood.
Half of all marine rubbish in the tropics is man-made, with the proportion far higher close to Antarctica, where there are no forests to provide natural flotsam, he says.
The kinds of organisms found on litter are not just species like barnacles, which commonly attach to the bottom of ships.
"There are weedy species a bit like cold water corals, together with more familiar species like molluscs and bivalves," Dr Barnes told the BBC.
Marine life has used natural debris to spread and colonise new habitats for millions of years.
"Most of these organisms would be able to disperse anyway by larvae," he said.
"But larvae travel for relatively short distances. They wouldn't be able to invade areas which are too different from the areas that they live in.
"But when larvae settle on to plastic, they metamorphose into adults and as adults they can survive much harsher ranges of conditions," he said.
Double threat
Human rubbish spreads across all the world's seas, forming half of all the marine debris washing up in the tropics and more at higher latitudes.
The continent could be at particular risk from alien species floating in because of a double threat from global warming and a lack of alternative habitats for many of its species.
Outside organisms floating in could benefit from warmer conditions and displace the indigenous species, many of which do not occur anywhere else in the world.
"There has always been marine debris in the form of pumice, volcanic rock, coconuts and so on [but] we are greatly increasing something that was already there.
"Antarctica is one of the places which is most threatened," Dr Barnes said.
He and his colleagues are continuing research into the effects of this increased migration.