Tests on more than 100 sea turtles in the Pacific Ocean, Atlantic Ocean and Mediterranean Sea have revealed microplastic in the gut of every single turtle – including off the coast of Queensland.
More than 800 synthetic particles were found in the 102 turtles studied, with up to 20 pieces of microplastics (synthetic particles less than 5mm in length) found in each of the turtles sampled from Queensland. However, researchers only tested part of each animal's gut – so the total number of particles is estimated to be about 20 times higher.
James Cook University's Associate Professor Mark Hamann was one of two Australian researchers involved in the study.
"Ingestion of plastics is not the main threat to the species, but its presence in every turtle is a concern," he said.
"The issue is worthy of continued investigation as we suspect that the younger turtles are more vulnerable and we don't know what effects microplastic ingestion will have on them."
The most common microplastics were fibres, which can potentially come from sources including clothing, tyres, cigarette filters and maritime equipment such as ropes and fishing nets, with the Queensland turtles also found to have microbeads in their gut, which is believed to be the first isolation of microbeads from a sea turtle.
"Their small size means they can pass through the gut without causing a blockage, as is frequently reported with larger plastic fragments," said lead author Dr Emily Duncan from the University of Exeter.
"However, future work should focus on whether microplastics may be affecting aquatic organisms more subtly. For example, they may possibly carry contaminants, bacteria or viruses, or they may affect the turtle at a cellular or subcellular level. This requires further investigation."
Researchers do not currently understand how synthetic particles are ingested by turtles, but the likely sources are polluted seawater and sediments, and eating via prey or plants.
The study included all seven species of marine turtle, with the samples taken from ones that had died by stranding or bycatch. The study sites were North Carolina, USA (Atlantic), Northern Cyprus (Mediterranean) and Queensland, Australia (Pacific).
The turtles with the most synthetic particles were in the Mediterranean – thought to have higher rates of contamination than the Atlantic or Pacific – but this study's sample sizes and methodology did not allow for detailed geographical comparisons.
"Microplastic ingestion ubiquitous in marine turtles" was published today in the journal Global Change Biology and was led by researchers from the University of Exeter and Plymouth Marine Laboratory, working with the Greenpeace Research Laboratories.
