Faculty Advisor

Hodum, Peter

Area of Study

Science and Mathematics

Publication Date

Summer 2018


For the past 30 years, plastic pollution research has used plastic ingested and retain in seabirds’ gastrointestinal (GIT) tract as indicators of pollution on different spatial and temporal scales. Types and size of plastic found in birds’ stomachs were used to determine pollution types and severity at different times and places. However, the length of time that birds can retain plastic in their GIT is unknown, making ingested plastic’s use as a bioindicator questionable. We assessed retention times in two seabird species, the Northern Fulmar (Fulmarus glacialis) and the Cassin’s Auklet (Ptychoramphus aleuticus), and compared the size and density of pieces of plastic in juveniles and adults of each species. Juveniles have a known time of ingesting plastic (fledging to when they died) while adults have an unknown time. We predicted that if retention times were long, the adults would have smaller and greater density plastic than juveniles due to grinding in the GIT wearing down pieces. If retention times in juveniles and adults were similar, the size and density of plastic pieces would be similar. Plastic from fulmars were similar size in both age groups, suggesting that fulmars do not retain plastic for long. Adult auklets’ GIT contained smaller pieces than juveniles, indicating longer retention times. The method provides a protocol to assessing wear and thus retention times of plastic either retrospectively using archived samples or from new samples.


University of Puget Sound