In the worst case, a researcher said Friday, a 5.3-meter (17-foot) young sperm whale beached on the Aegean island of Mykonos had swallowed 135 plastic items weighing a total of 3.2 kilograms (7 pounds). This blocked its stomach, grossly distending it, while the animal itself was emaciated and had starved to death.
Sperm whales are an endangered species already at high risk in the Mediterranean from deadly collisions with ships, entanglement in drift fishing nets and noise pollution from oil and gas exploration.
The study published in the Marine Pollution Bulletin, which organizers say was the first on such a scale in the Mediterranean, found that sperm whales were also the species worst affected by plastic ingestion. Six out of ten specimens were found to have consumed plastics according to Alexandros Frantzis, scientific director of the Athens-based Pelagos Cetacean Research Institute that conducted the research.
"The amount of (debris) we found is very high, and should set off an alarm," he told The Associated Press. "It is now something common. ... It's not just that some random animal swallowed plastic."
Frantzis is a prominent whale and dolphin expert known for first linking fatal whale beachings to the use of military sonar by warships.
In a separate incident outside the scope of the Greek study, an 8-meter (26-foot) pregnant sperm whale was found dead off Sardinia in March with 22 kilograms (48.5 pounds) of plastic in its stomach.
The study, which did not examine microplastics that are invisible to the naked eye, found that nine out of 34 whales, porpoises and dolphins washed up dead on Greek shores from 1993-2014 had swallowed plastic debris of considerable size. Three died from it.
Frantzis said bags pose a huge problem because, while not more lethal than other plastic items, they are so widely used.
"None of us is innocent," he said. "Without our knowledge or intent, some of (the plastic that is swallowed by whales or dolphins) may have passed through our hands. We may even have disposed of it in the trash, and it may have been blown away from an open landfill. These things travel, they have no borders."
The Mediterranean is one of the most polluted seas in the world in terms of both floating and seabed debris, with plastic the main problem — found even in abyssal depths. The World Wide Fund for Nature and Greenpeace have both expressed grave concern.
Frantzis said the solution is to stop the "crazy and useless" production of plastic.
"Don't buy, don't use (it) and exert pressure to stop the production," he said.