Madrid – The plastic waste washed up on beaches and floating on the water surface is only the tip of the iceberg when it comes to the litter dumped into European seas, a study published by environmental organization Oceana in Madrid on Friday shows.

A threat to marine life

Visible plastic waste only accounts for 1 per cent of the total, Oceana warned, while 99 per cent of plastics in European deep seas end up on the sea floor, "threatening areas of high biological value, such as seamounts, canyons and escarpments."

The Mediterranean is especially at risk due to the high population density in adjacent states, the high water depth and a low level of water exchange.

Plastic litter is dragged down by underwater currents, the authors explained, predicting that it will take centuries for it to decompose in dark and cold regions hundreds of metres below the surface.

A graphic shows the plastic pollution in the ocean

Less plastic, less waste

The director of the plastics campaign at Oceana in Europe, Natividad Sanchez, emphasized that cleaning the beaches and collecting plastic waste from the water surface was "crucial" but entirely insufficient.

"It is essential that we reduce the manufacture of single-use plastics," she said, criticizing an EU directive on the matter from June last year as insufficient.

The EU is planning a levy on plastics from next year, partly in a bid to reduce the amount of waste.

Environmental organization WWF last year estimated more than 500,000 tons of plastic lands in the Mediterranean annually, the equivalent of 33,800 plastic bottles per minute.

Egypt, Italy and Turkey were the worst offenders, it said.