Thursday, October 20, 2016

Hawaiian shearwaters have a bellyful of plastic marine debris

Not just seabirds: An entangled Hawaiian monk seal.  Credit: NOAA.

Laysan albatross chicks have been found dead with their bellies stuffed with bits of plastic, and a new study shows that Kaua`i-based Newell’s and wedge-tailed shearwaters face similar threats.

Worse, the amount of plastic found in the seabirds is increasing over time.

“On Kaua‘i…50.0 % of Newell’s…and 76.9 % of wedge-tailed shearwater … fledglings necropsied during 2007–2014 contained plastic items in their digestive tract, while 42.1 % of adult wedge-tailed shearwaters had ingested plastic'

That is one conclusion of the paper, “Plastic ingestion by Newell’s (Puffinus newelli) and wedge-tailed shearwaters (Ardenna pacifica) in Hawaii.” It was published in the journal Environmental Science and Pollution  Research by Elizabeth C. Kain, Jennifer L. Lavers, Carl J. Berg, Alexander L. Bond and Andr√© F. Raine. 

The researchers also found that “For both species, the frequency of plastic ingestion has increased since the 1980s with some evidence that the mass and the number of items ingested per bird have also increased.”

In fact, hundreds of marine species are threatened by plastic, which can mimic natural food sources, or be mistaken for food by seabirds, turtles, squids, fish, oysters, seals and others. 

The researchers in this paper looked at the stomach contents of seabirds killed by predators or collisions in the 2013-2014 nesting season. The results were compared with a study done in the 1987 season on Kauai, when 11 percent of the birds were found to have eaten plastics. For Newell’s shearwaters, that represents nearly a five-fold increase over  a quarter century.

In both the Newell’s, a mountain-nesting bird, and the wedge-tailed shearwaters, which nest near the shore, the predominant color of ingested plastic was white.

Both adults and fledglings had plastic in their guts. Since fledglings receive all their food regurgitated by their parents, the parents are presumed to have been delivering plastic-laced meals to their young.

“Plastic ingested by seabirds has been shown to block and take up space in the digestive tract, contributing to dehydration and in some cases starvation,” the authors wrote.

There is also suggestion in the scientific literature that the plastic can release chemical pollutants into the bodies of the birds, they said.

“The amount of plastic in the oceans is increasing and poses an increased risk of entanglement, ingestion, and thus morbidity and mortality for marine life,” the authors wrote.

National Geographic last year had a story that suggested that every seabird on the planet has or shortly will have a plastic ingestion issue.

That story references this study, which makes the point that “this threat is geographically widespread, pervasive, and rapidly increasing.”

© Jan TenBruggencate 2016

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