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Dolphins are exhaling microplastics through their blowhole
Microplastics are everywhere. From the remotest areas of the planet to within our own bodies, these tiny polymers are an inescapable part of the modern world.
New research on dolphins suggests that they’re even in the animal’s breath.
Plastics found in water bottles and clothing are being exhaled by dolphins.
Tests on 11 of the marine mammals in Florida and Louisiana, USA, revealed that the breath of every single animal had at least one piece of microplastic in it. These ranged from plastic fibres to fragments and films, made from a wide variety of materials including polyethylene and polyester. It seems likely the plastics are entering the dolphins’ lungs through contaminated water and air.
While the effects on the health of dolphins are currently uncertain, the fact that the marine mammals are inhaling and exhaling plastics has alarmed scientists. Dr Miranda Dziobak, lead author of the research, says their findings are a reminder of “how extensive environmental microplastic pollution is.”
“The dolphins we studied were living in an urban estuary and a rural estuary, but we found microplastics in breath samples collected from both sites,” Miranda says. “This demonstrates that, just as other researchers found, that airborne microplastics are everywhere.”
“As dolphins have a much larger lung capacity than humans, and take really deep breaths, they may inhale much higher doses of microplastics than humans. As human studies have shown that microplastic inhalation can lead to lung inflammation and other respiratory problems, dolphins may be even more vulnerable to these health impacts.”
The findings of the study were published in the journal PLOS One.
Dolphins living in Sarasota Bay has been studied for over 50 years. © Brad Meece/ Shutterstock
How do plastics affect dolphins?
The dolphins of Sarasota Bay on the west coast of Florida have been studied for decades as part of the longest-running study of wild dolphins. Since 1970, the project has documented the lives of six generations of these animals which live in the waters year-round.
This has helped scientists learn a lot about the lives of dolphins, from their behaviour to the ways they grow and communicate.
One of the many researchers who has studied them over the years is Miranda, who worked with the Sarasota Dolphin Research Program to investigate how pollution is affecting these animals.
“We have been studying exposure to plastic pollution and chemical additives in dolphins for almost 10 years now,” she says. “The types of chemicals these dolphins are exposed to point towards a plastic origin, so our recent studies have focused on how dolphins may be exposed to plastic.”
“We’ve been exploring what the dolphins have been ingesting for the past couple of years, finding microplastics in their stomach contents and prey fish.”
As the dolphins eat microplastic-contaminated fish, levels of the pollutant build up in their bodies. However, it’s not the only way that plastics get into the marine mammals.
Emerging research has shown that microplastics can travel through the air. This made it possible that the dolphins weren’t just eating plastic, but potentially breathing it too.
As part of regular, licensed check-ups of the dolphins, the researchers took breath samples using a petri dish. © Todd Speakman / National Marine Mammal Foundation, licensed under CC BY 4.0 via EurekAlert!
Breathable plastics
As regular health check-ups are carried out on the Sarasota dolphins, Miranda and the other researchers looked to see whether plastics had entered their lungs. During these check-ups, the dolphins are safely held in the water to allow tests to be carried out before being released.
First, the researchers cleaned the blowhole and the skin surrounding it to ensure that there weren’t any microplastics on their surface that might be swept up during breathing. The researchers then held a petri dish over the blowhole as the mammals breathed out to capture any microplastics from inside the dolphins’ lungs and airways.
Using additional breath samples from dolphins in Louisiana’s Barataria Bay, the microplastics were then examined. More than half were made of polyethylene, while another quarter of the sample were polyester fibres.
Though it’s impossible to know exactly where the plastics have come from, the presence of nearby urban areas suggests that the microplastics might be blown out to sea and over the bay, where dolphins can breathe them in.
These microplastics could also have come from water entering the bay that’s contaminated with microplastics, whether that’s from sewage spills, cleaning water or a myriad of other sources. This can then become airborne through the action of waves, with the microplastic-contaminated sea spray available to be breathed in by dolphins and other air-breathing animals.
Richard Sabin, the Principal Curator of Mammals at the Natural History Museum, says that he expects many other species are probably breathing in plastics too.
“I am not at all surprised by the results of this study,” says Richard, who was not involved in the research. “We’ve known for a while that microplastics are present in the diet of these animals. Even a spectacled porpoise, which only lives in remote areas of the southern hemisphere, was found to have plastics in its gastrointestinal tract when it was brought to the Museum in 2017.”
“We now know that these plastics can be found in the breath of dolphins. I’m sad to say that I would expect the findings to be similar for large baleen whales too.”
As the study’s sample size was small, the scientists hope that future research will focus on expanding the number of animals used, as well as investigating microplastics in other species.
