Thursday, October 29, 2009

Where Do Albatrosses Find the Plastic?

Most readers of this blog have probably already seen Chris Jordan's sad photos of dead albatross chicks that ingested too much plastic. The albatrosses featured at that page were found on the Midway Atoll. Their parents found bits of plastic, thought they were food, and brought them back to feed to their chicks. Some albatross chicks regurgitate the plastic later, but many suffer detrimental effects. A chick that ate too much plastic would eventually starve to death, as these chicks did.

So where do they find the plastic? Albatrosses forage by wandering great distances over the ocean and picking up likely prey items. The bits of plastic were most likely floating in the well-documented garbage patches of the Pacific Ocean. A new paper in PLoS ONE suggests that the problem for Laysan Albatrosses is far worse in the western Pacific than in the eastern Pacific.

The authors studied two albatross breeding populations, one at Oahu in Hawaii and the other at Kure, 2,150 km to the northwest. They tagged adults in each colony with geolocators to track their movements during and after the breeding season. As the chicks fledged, they collected and examined the chicks' boluses, regurgitated material that includes any non-digestible items that the chicks swallowed. This could include bones, beaks of squid, or plastics.

Data from the geolocators showed that the adults from the two colonies foraged in different parts of the Pacific. The Kure colony mostly foraged to the north and west of Kure; Oahu albatrosses foraged to the north and east.

Contours show the foraging ranges for albatrosses on Kure Atoll (blue) and Oahu (red) during the a) incubation b) chick guard c) post-guard and d) non-breeding stages.

Examination of the boluses showed that chicks on Kure ingested and regurgitated a far greater amount of plastic than chicks on Oahu.

Comparison of a) natural food mass, b) plastic mass, c) # plastic pieces and d) average plastic piece mass from Laysan albatross boluses on Kure and Oahu.

From the article:
The finding that birds breeding on Kure Atoll fed their chicks, on average, ten times more plastic than birds breeding on Oahu suggests that putative Western Garbage Patch where the majority of Kure birds foraged may in fact be a just as much of a threat to marine life as the frequently discussed Eastern Garbage Patch. Furthermore, every bolus examined from Kure Atoll contained multiple pieces of fishing paraphernalia, while only two boluses on Oahu contained any evidence of fishing line or tools (despite recreational fishing adjacent to the breeding colony on Oahu), suggesting that the threat from fisheries not only comes from bycatch for this species but also from the consumption of fishing gear. It is unclear whether the Western Garbage Patch contains more trash than the Eastern Garbage Patch, or if the size and composition of the pieces are easier for the birds to ingest compared to those found in the Eastern Garbage Patch in addition to the finding that albatrosses from Kure spend a greater proportion of time foraging in this area.
The authors also raise a third possible explanation. The colony at Kure has a higher population density, so adults there may need to be less selective in choosing food items.

Whether this will help scientists prevent albatrosses from ingesting so much plastic remains to be seen. There is such a tremendous amount of plastic floating in the Pacific that there seems to be little hope of removing it. Perhaps someone will find an alternative solution. In the long term, reducing plastic use and plastic waste should cut down on albatross deaths. My hope is that albatrosses will eventually learn to distinguish plastic from food.

Images are reproduced from PLoS ONE and link to the originals.