Laysan albatrosses (Phoebastria immutabilis), which forage throughout the North Pacific, are well known for their tendency to ingest plastic. Their flexible foraging strategy has potentially led to a decrease in their foraging efficiency as they ingest large amounts of plastic, which is in turn fed to their chicks. It is unclear just how often Laysan albatrosses encounter or ingest plastic and whether plastic is mistaken for prey, has natural food attached to it, or is consumed to assist in digestion as is sometimes done with pumice. Unfortunately, plastic ingestion leads to mechanical blockage of the digestive tract, reduced food consumption, inappropriate satiation of hunger, and potential exposure to toxic compounds. While there have been documented detrimental effects on the growth rates and fledging masses of chicks, it is still unclear what levels of mortality are caused by plastic ingestion. What is clear, however, is the source of the plastic: there is now so much floating marine debris accumulated in the North Pacific gyre that is it known as the "great garbage patch". This patch consists of high densities of floating plastic debris, particularly between 20° and 40° N, within a few hundred kilometres of the coast and in the gyre centres, between the tropical and subarctic waters. This area of concentrated debris consists of two accumulations: the "Western Garbage Patch" that occurs off Japan and the"‘Eastern Garbage Patch" located between Hawaii and California. These accumulations correspond to the locations of two sub-gyres within the North Pacific Gyre connected by a narrower band of marine debris north of the Hawaiian Archipelago (where 99% of Laysan Albatrosses breed). (Young et al. 2009 and references therein)
Young et al. (2009) investigated the questions of whether Laysan albatrosses nesting on widely separated islands (Kure Atoll and Oahu Island, separated by 2,150 km) exploit resources closer to their breeding colonies during the breeding season, how their foraging locations change throughout the reproductive cycle, and whether this leads to differences in plastic ingestion as represented in their boluses (regurgitated undigestable material). Determining how and where marine organisms come into contact with marine debris could have implications for the design of management strategies that mitigate its environmental impact. To track foraging behavior and plastic ingestion, Young et al. combined the use of electronic data logging devices to determine the at-sea distributions of adults with the collection of chick boluses to evaluate differences in plastic ingestion. The authors found that chicks from Kure Atoll were fed almost ten times the amount of plastic relative to chicks from Oahu despite boluses from both colonies having similar amounts of natural food. Foraging adults from Kure had a greater overlap with the putative range of the Western Garbage Patch, possibly explaining the higher plastic loads at this colony. 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.
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