The valleys and canyons beneath the seas around Europe are filling with rubbish which is disrupting and destroying marine life, according to a scientific study published on Wednesday.

A A plastic bag in the Arctic harbouring sponges and shrimps
B Litter trawled from a Mediterranean canyon
C A beer can from the Atlantic
D A Mediterranean plastic bag
E “Express Rice” packet off the coast of Scotland
F Net entangled in coral off Scotland

In a project coordinated by the University of the Azores, a group of scientists examined data collected from 32 sites at depths from 35 to 4,500 metres. The results painted a bleak picture.

According to the study some 6.4 million tonnes of litter enter the world’s oceans each year forming what has been called “a seventh continent of plastic”.

The authors of the study, which appeared in the journal “Plos One”, noted that the litter looks bad and is harmful too.

Many marine species mistake rubbish for food. Discarded fishing gear, which made up some 34 per cent of the litter, based on weight, can entangle and kill mammals, turtles, birds and corals. Many fish are victims of “ghost fishing” by nets that are no longer harvested by humans. Floating litter also disturbs the marine ecosystem by transporting species, like barnacles, to new habitats.

The study made use of new methods which allowed the scientists to explore the Atlantic seabed with video from robot vehicles, which could also pick up objects, and cameras towed by boats. In the Mediterranean old-fashioned trawling was also used to drag up litter. The scientists listed glass, metal, wood, paper, cardboard, clothes, pottery as well as "unidentified materials ".

Of all the many types of litter that end up in the sea, the most abundant is plastic, which made up 41 per cent of the rubbish identified in the survey. Plastic bags were the most common items found by the researchers. Plastic is water-repellent and long-lasting and generates toxic chemicals that can kill marine life.

Fishing gear tends to be discarded in shallower water, in areas where the fish population is densest. Plastic is found offshore near places where the human population is densest and, carried by currents, accumulates in deep ocean canyons.

"The Mediterranean, particularly near large population centres, is the European zone most affected," François Galgani, a researcher at French Research Institute for Exploitation of the Sea and the co-author of the report, told Reuters.