The estimate comes from French and Belgian marine biologists who analysed water samples taken in July off France, northern Italy and Spain to a depth of 10-15 centimetres (four to six inches).
French Institute for Exploration of the Sea (Ifremer) made rough estimation of roughly 250 billion pieces of micro-debris in all the Mediterranean sea.
The figure derives from 4,371 minute pieces of plastic -- average weight 1.8 milligrams (0.00006 of an ounce)found in the samples.
The sampling only covered surface waters and is a preliminary evaluation. Further samples, off Gibraltar, Moroccow, Algeria, Tunisa, Sardinia and southern Italy, will be taken in 2011 to get a wider picture.