Nearly 50 percent of the sea turtles that they examined ate macroplastic, and most who ingested a plastic type ate multiple pieces.
A study of animal mortality due to the ingestion of marine plastics has found that sea turtles ingest more and die from micro and macroplastic ingestion than marine mammals and sea birds.
The researchers write in their study that nearly 50 percent of the sea turtles that they examined ate macroplastic, and most who ingested a plastic type ate multiple pieces. Many of the turtles examined had more than 10 pieces of hard plastics, soft plastics and fishing debris in their stomachs.
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The size of these ingested plastics were mostly small (mean piece size = 0.22 cm3). More than half of the individuals in the study had plastics that were 1 cm in size. Of the sea turtles in the study, 8.4 percent of the deaths were attributed to the ingestion of the plastics. The researchers called this known debris deaths, or KD. the researchers categorized 0.8 percent of the deaths of these reptiles as PD or probable debris deaths.
Plastic Loads
The researchers note that a single, adult individual sea turtle with a plastic load of 93 pieces at a length of ≥5mm has a 50 percent chance of death, while a turtle with a plastic load of 342 pieces of plastic at ≥5mm in length had a 90 percent chance of mortality.
Small juveniles with a plastic load of 105 pieces at ≥5 mm in length had a 50 percent chance of death while those with a load of 377 pieces of plastic at ≥5 mm in length had a 90 percent chance of death.
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Of all the animals studied, (marine mammals, sea birds) sea turtles fared the worst when it came to plastic ingestion and death. The researchers said that nearly 50 percent of the sea turtles in their study had ingested plastic, while 35 percent of the sea birds and 12 percent of the marine mammals had ingested plastic.
Sea Turtle Deaths From Plastics
Ingested plastic was the cause of death in 4.4 percent of all the necropsied turtles in the study, with almost all of the deaths occurring in post hatchlings and juveniles. The researchers note that the green sea turtle(Chelonia mydas), which was well represented in their study, have a more generalist diet which could contribute to the increase and types of plastic that they ingest. The juveniles tend to ingest plastics at more frequent occurrences than adult sea turtles because the juveniles encounter more plastic at higher rates than adults. This can be attributed to the higher deaths of post hatchlings and juveniles examined in the study.
The researchers are with the Ocean Conservancy, Institute for Marine and Antarctic Studies, University of Tasmania, Ecology and Conservation in the Anthropocene (ECOA) Lab, Instituto de Ciências Biológicas e da Saúde, Universidade Federal de Alagoas, Alagoas, Brazil, and the Department of Ecology and Evolutionary Biology at the University of Toronto.
The complete study, A quantitative risk assessment framework for mortality due to macroplastic ingestion in seabirds, marine mammals, and sea turtles,” can be read on the Proceedings of the National Academy of Sciences website.
