A First Attempt at Modeling the Global Reservoir of Plastic in Biota: A Case Study With Sea Turtles

Abstract Marine wildlife ingest plastic, making them a reservoir for plastic debris. To date, we lack estimates of how much plastic resides within marine animals globally, making it difficult to reconcile the fate of plastic in the global ocean. To help fill this knowledge gap, we collected data on amount of plastic debris found in sea turtles necropsy studies from the scientific literature up until 1 January 2020. We aimed to use this data ( n = 60), along with predictor variables, in a regression model to quantify how much plastic resides within sea turtles globally. We found that geographic (absolute latitude), socio‐economic (income of country), and ecological (species name) indicators significantly correlate with how much plastic is found in sea turtle gastrointestinal tracts. Our multispecies model suggests that leatherback turtles ( Dermochelys coriacea ) contain the most plastic in their gastrointestinal tracts, and loggerhead turtles ( Caretta caretta ) contain the least. This presents one of the first attempts to understand which sea turtle species has the highest propensity for plastic ingestion. Due to limited data, we were only able to estimate the amount of plastics that reside in female green turtles ( Chelonia mydas ) globally for a snapshot in time. Here, we provide the first estimate of a global marine animal reservoir of plastic– we estimate that at any given time, female green turtles carry 5.6–6.4 tonnes of plastic in their gastrointestinal tracts. We discuss future research directions to help reduce the uncertainty surrounding this estimate and fill in the gaps for other species.