Use of indicator chemicals to characterize the plastic fragments ingested by Laysan albatross

Laysan albatross (Phoebastria immutabilis) ingest plastic marine debris of a wide range of shape, sizes and sources. To better characterize this plastic and provide insights regarding its provenance and persistence in the environment, we developed a simple method to classify plastic fragments of unknown origin according to the resin codes used by the Society of Plastics Industry. Known plastics were analyzed by gas chromatography-mass spectroscopy (GC-MS) to identify indicator chemicals characteristic of each plastic resin. Application of this method to fragments of ingested plastic debris from boluses of Laysan albatross from Kure Atoll, Hawai'i, yielded proportions of 0.8% High Density Polyethylene, 6.8% Polystyrene, 8.5% Polyethylene Terephthalate, 20.5% Polyvinyl Chloride and 68.4% Polypropylene. Some fragments were composed of multiple resin types. These results suggest that infrequently recycled plastics are the dominant fragments ingested by albatross, and that these are the most prevalent and persistent resin types in the marine environment.