Polymer Identification of Plastic Debris Ingested by Pelagic-Phase Sea Turtles in the Central Pacific

Pelagic
Pacific sea turtles eat relatively large quantities of
plastic (median 5 g in gut). Using Fourier transform infrared spectroscopy,
we identified the polymers ingested by 37 olive ridley, 9 green, and
4 loggerhead turtles caught as bycatch in Hawaii- and American Samoa-based
longline fisheries. Unidentifiable samples were analyzed using high-temperature
size exclusion chromatography with multiple detectors and/or X-ray
photoelectron spectroscopy. Regardless of species differences in dive
depths and foraging strategies, ingested plastics were primarily low-density,
floating polymers (51% low-density polyethylene (LDPE), 26% polypropylene
(PP), 10% unknown polyethylene (PE), and 5% high-density PE collectively).
Albeit not statistically significant, deeper diving and deeper captured
olive ridley turtles ate proportionally more plastics expected to
sink (3.9%) than intermediate-diving green (1.2%) and shallow-diving
loggerhead (0.3%) turtles. Spatial, but no sex, size, year, or hook
depth differences were observed in polymer composition. LDPE and PP,
some of the most produced and least recycled polymers worldwide, account
for the largest percentage of plastic eaten by sea turtles in this
region. These novel data inform managers about the threat of plastic
ingestion to sea turtles and may motivate development of more environmentally
friendly practices for plastic production, use, and waste management.