Cory's shearwater was the species with the highest level of ingested plastic
A new study has discovered that 94 per cent of Cory's shearwaters on the Catalan coast have ingested plastic. In the case of Yelkouan and Balearic shearwaters, the conclusion is that 70 per cent of studied birds were similarly affected. Jacob González Solís from the Department of Animal Biology and the Biodiversity Research Institute (IRBio) of the University of Barcelona (UB), headed a research group that carried out the study, published in the Marine Pollution Bulletin.

Plastic pollution is known to be a threat for marine ecosystems around the world, but it has not yet been extensively studied. Solís explained that, "this is the first assessment of plastic ingestion in Mediterranean seabirds. The Mediterranean Sea has been recognised as a singularly sensitive ecosystem because its coast is very industrialised, shipping activity is intense and it contains high density floating plastic areas."

Floating plastic debris can cause entanglement, ulcers, infections and death in marine animals. They can ingest them by mistake, because plastic fragments resemble their natural food items such as jelly fish, or take them in by eating prey which has in turn consumed plastic. Ingested fragments found were filaments, plastic spheres, laminar plastic and industrial pellets.

The study was based on the analysis of 171 birds accidentally caught by longliners on the Catalan coast from 2003 to 2010. The UB research group studied plastic ingestion in nine particularly endangered seabird species: Cory's shearwater, Yelkouan shearwater, Balearic shearwater, gannet; Audouin's gull, Mediterranean gull, yellow-legged gull, black-legged kittiwake and great skua.

Results showed that 66 per cent of the seabirds had at least one piece of plastic in their stomachs.

"Results are alarming," said Solís. "All three of the worst affected birds are of conservation concern, particularly the Balearic shearwater, which is listed as critically endangered. There are only around 3,000 breeding pairs in the world."

Seabird chicks are the most vulnerable to plastic ingestion as they cannot regurgitate as adults do. The lower occurrence of plastics in gulls probably results from their greater ability to regurgitate any hard remains. The study proves that plastic trash - most of it from recreational activities - is a global problem as it enters the oceans' food chain and becomes a threat for seabirds and marine ecosystems.

"Plastic floats and is difficult to degrade," said Solís. "Eventually, all pollutants which are not destroyed on land arrive in the sea. But the sea is not a rubbish bin. The control over plastic production and transportation at industrial level has probably improved, but there is an urgent need to develop stricter controls on waste dumping and to prohibit ships from discharging into the sea."

Source: Marine Pollution Bulletin.