Assessment of Plastic Ingestion and Persistent Organic Pollutants in Sea Turtles across the Pacific Ocean

Abstract

Plastic debris is a growing concern for many marine organisms due to entanglement, ingestion, and exposure to toxic chemicals. The increasing presence of micro and macro plastics in our environment threatens marine animals, especially sea turtles, as their tendency to investigate, pry into, or eat floating debris is substantial. I examined plastic ingestion rates and frequency of ingestion of 38 sea turtles [3 leatherback (Dermochelys coriacea), 3 loggerhead (Caretta caretta), 6 green (Chelonia mydas) and 26 olive ridley (Lepidochelys olivacea) sea turtles] that were incidentally captured in Hawaiian and American Samoan longline fisheries and quantified the amounts, types, sizes, and colors of ingested plastics in their gastrointestinal tracts. Additionally, I hypothesized that ingestion of plastic debris is a potential source of exposure of persistent organic pollutants (POP) to threatened pelagic sea turtles of the Pacific Ocean, by first providing baseline POP contaminant data for pelagic Pacific sea turtles and then correlating these data with plastic ingestion amounts. Ingested plastic was found in 87% (n = 33) of the turtles, with no plastic found in the 3 leatherback turtles, in 1 adult loggerhead, and in 1 juvenile green turtle. Mean dry mass of ingested plastic in all turtles sampled was 9.68 g with a range of 0.0185 g to 64.2 g amongst turtles that ingested plastic. The percentage of individual total gut contents comprised of plastic ranged from 0.00113% to 8.16% amongst turtles with ingested plastic and a mean of 1.01% in all turtles sampled. Juvenile green turtles ingested significantly more plastic than other species. Additionally, adipose samples from 25 of the turtles (2 loggerhead, 6 green, 17 olive ridley) were analyzed by gas chromatography/mass spectrometry for 83 polychlorinated biphenyls (PCBs), 20 organochlorine pesticides, 32 brominated flame- retardants and by liquid chromatography tandem mass spectrometry for hexabromocyclododecane (HBCD). I analyzed differences among species, sex, and correlations with turtle length and capture locations. Total dichlorodiphenyltrichloroethanes (DDTs) were the predominant POP in both loggerhead (mean = 18.3 ng/g wet mass) and olive ridley (15.8 ng/g wet mass) turtles, and the second highest POP class in green turtles (1.80 ng/g wet mass). Total PCBs were the predominant POP in green turtles (2.71 ng/g wet mass), yet they had lower total PCB concentrations than loggerhead (4.92 ng/g wet mass) and olive ridley (3.95 ng/g wet mass) turtles. Green turtles had the highest concentrations of α-HBCD (1.46 ng/g wet mass), which was the only detected HBCD isomer. Among olive ridley turtles, few sex differences were seen in POP concentrations, likely because sampled turtles were mainly juvenile. Concentrations of several POPs increased with straight carapace length of olive ridleys, suggesting bioaccumulation through age. A geographic gradient was observed with concentrations of several POPs increasing with capture latitude. Plastic ingestion is extremely common in sea turtles and effects of toxic chemicals could have detrimental effects on their health and survival. Amounts of ingested plastic were unrelated to POP concentrations, suggesting that sea turtle exposure to POPs is predominately through their natural food chain rather than from ingested plastics.