Microplastics found in 99 percent of tested sea turtles' internal organ tissue

Microplastics are showing up in more and more places where they were never meant to be. This time, it’s inside the organs of sea turtles, including in their reproductive systems.

That’s the troubling conclusion of a new study that examined stranded loggerhead sea turtles and found tiny plastic particles throughout their bodies.

Sea turtle bodies full of microplastics

The research, conducted by scientists from the University of Manchester, focused on 10 turtles that were accidentally caught in fishing nets and later recovered by the Oceanogràfic Foundation of Valencia.

The team discovered significant levels of microplastics in male reproductive tissues and found the particles in other major organs in both male and female turtles.

These included the heart, kidneys, liver, spleen, stomach, intestines, skeletal muscle, subcutaneous fat, and even the brain.

Microplastics reach turtle fertility organs

This is the first study to offer direct evidence that microplastics can travel from the gut to other parts of the body in sea turtles.

The findings suggest that these particles don’t just pass through the digestive system – they may end up accumulating in places that are critical to the animals’ health and reproduction.

“Microplastics are a pervasive marine environmental pollutant, on a par with other global threats such as climate change and ozone depletion,” said lead author Leah Costello, a Ph.D. researcher at the University of Manchester.

“Our study is the first to show direct evidence of the presence of microplastics in the reproductive and other organs of loggerhead sea turtles.”

Sea turtles already face many pressures from human activity and although we have been aware that they ingest plastic throughout their range, the finding of microplastics in almost every tissue sample was quite shocking.

“These findings show that even seemingly healthy individuals could be under physiological stress, impacting the reproductive success of vulnerable and recovering populations,” Costello continued.

Scale and composition of the pollution

The analysis found that nearly every tissue sample – 98.8% to be exact – contained foreign microparticles. Around 70% of those were identified as microplastics.

The most common types were polypropylene, polyester, and polyethylene.

Polypropylene is often used in food packaging, bottle caps, ropes, and personal care products, all of which can end up in the ocean.

Polyethylene, the material used in plastic bags, poses a direct threat to turtles that often mistake it for jellyfish and ingest it directly.

Size-wise, the largest median particles (about 25 microns) were found in the intestines and fat tissue. The smallest particles (around 15 microns) showed up in the stomach and reproductive organs.

Polyester microfibers, shed from clothing, are also a major contributor to marine pollution. In a particularly striking finding, the scientists visually confirmed cotton microfibers embedded in heart tissue.

Long-term impact of microplastics

Each year, an estimated 3 million tons of primary microplastics are released into the environment. On top of that, another 5.3 million tons of larger plastics break down into smaller particles over the same time.

Sea turtles, which can retain plastics in their digestive systems for up to four months, may be absorbing these particles into their bloodstream, allowing them to spread to other organs.

The potential health consequences could be serious. Microplastics have already been linked to inflammation in other animals, and similar effects are suspected in turtles.

“Microplastic accumulation is likely to be associated with organ damage and toxicity in these incredible marine reptiles that can live for 70 years,” said co-author Professor Holly Shiels from the University of Manchester.

“Of particular concern is the impact on reproduction, with implications on growth, development and viability of offspring which could spell trouble for the stability of these already vulnerable sea turtle populations. However, further studies are required to more broadly assess the biological and health impacts of microplastic on sea turtle reproduction,” Shiels concluded.

Deeper problem than we realized

The findings raise urgent questions about how plastics are affecting wildlife far beyond the obvious signs of entanglement or ingestion.

These invisible microplastics could be disrupting key biological systems in turtles and other animals already under threat.

As research continues, what’s clear is that microplastics are not just a surface-level issue. They’re working their way deep into living creatures – sometimes right into the organs that are essential for species survival.

The full study was published in the journal Marine Environmental Research.

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