Ingested Plastic Causes Buoyancy Issues in Some Sea Turtles

Consuming plastic debris can lead to “floating syndrome,” especially in juveniles. Without intervention, many will not survive.

In March 2017, a green sea turtle was found floating and struggling to dive close to a pier near Clearwater, Florida. Weighing less than 3 pounds, the juvenile turtle was in critical condition when he was brought into Clearwater Marine Aquarium for rehabilitation. Three weeks later, the turtle — named Chex by rescuers — defecated a balloon with the ribbon still attached. Once the balloon passed, his buoyancy issues improved. After 66 days in rehabilitation, Chex was released into the wild.

Buoyancy issues represent one of many problems that plastic pollution can cause for sea turtles. Photo via Pxfuel.

Rescuers believe plastic debris caused his buoyancy issue — a problem faced by sea turtles that is sometimes called “floating syndrome.”

In recent years, sea turtles have become closely tied to the plastic pollution crisis, through images of turtles entangled in plastic or with straws stuck in their nostrils. Plastic can also impact turtles like Chex who accidentally ingest plastic and float on the surface of the ocean, unable to dive downwards. Without intervention, many of these turtles will die.

Plastic debris is a major threat to sea turtles. Marine biologists estimate that up to 52 percent of all sea turtles worldwide have ingested plastic. Plastic bags, for instance, can resemble swimming jellyfish, a favorite food for the reptiles. Recent research also found that sea turtles are attracted to the smell of plastic debris due to microorganisms, plants, and algae that accumulate on the plastics’s surface.

Once ingested, plastic can wreak havoc on a turtle’s body. Sea turtles are unable to regurgitate anything they swallow, so whatever they eat either passes through their body or gets stuck. When plastic accumulates in their body, it can block the gastrointestinal tract and cause a buildup of gas. This gas then causes the turtle to float.

While some turtles may be found by rescuers and rehabilitated, those who are not rescued are left unable to protect themselves from predation, boat strikes, dehydration, and sun exposure. Due to their inability to dive and a false sense of satiation caused by plastic in the stomach, turtles may also starve.

Turtles may be able to overcome buoyancy issues on their own if they pass the plastic material, but Stephen Menzies, curator at Reef HQ Aquarium in Australia, notes that they would have to survive the elements while the material passes.

Research into this issue appears to be limited and is complicated by the fact that sea turtles can float for a broad range of reasons, such as injuries from boat strike, infection, and changes in diet. Charles Manire, retired chief of rehabilitation at the Loggerhead Marinelife Center in Florida, also notes that sea turtles may voluntarily float when they are close to dying to prevent themselves from drowning.

Manire further explains that not all turtles that have plastic blocking their gastrointestinal tract will subsequently float. “The most common thing we see with plastic in the small turtles is blockage of the gastrointestinal tract. In some of those cases there may be a buildup of gas as well, but it’s not a consistent finding,” he says.

Plastic ingestion can cause long-lasting impacts to sea turtles even after the plastic material is passed. Fishing lines can cause damage to the gut walls, leading to secondary infection. “Even if it doesn’t kill them and passes through them, chemicals or other obstructions in the gut can weaken the animals and make [them] more susceptible to disease or ship strike,” says Kimberly Warner, senior scientist at Oceana.

The exact scale of this problem is unknown. Buoyancy issues caused by plastic ingestion encompass around “10 percent or less” of cases at The Turtle Hospital, a sea turtle rescue and rehabilitation center based in the Florida Keys, says Bette Zirkelbach, manager of the hospital.

“Flotation abnormalities are relatively common,” but those caused by plastic ingestion are “not overly common,” says Terry Norton, director and veterinarian at the Georgia Sea Turtle Center, a sea turtle education and rehabilitation facility

Menzies notices regional differences in the scale of buoyancy issues caused by plastic ingestion. “My observation is that in more developed areas of the Australian coast, where there is more plastics in the ocean, local populations are impacted more,” he says.

Manire says he sees juvenile turtles impacted by plastic ingestion more commonly than adult turtles in his region. “It takes a pretty large piece of plastic to block the intestines of a larger turtle and most of the plastic we deal with is very small,” he says. “The most common problem we see in larger green turtles in Florida are buoyancy problems caused by gas accumulation in the intestinal tract, but there is rarely evidence of marine debris involved.”

Experts believe younger turtles are more likely to be impacted by plastic ingestion due to their smaller body size and increased likelihood of ingesting debris. Young sea turtles travel on currents and spend their early years in the open ocean, but these currents are now home to high quantities of plastic, according to an August 2021 study. The authors state that the juvenile turtles’ location in the open ocean makes it difficult to assess the impacts of human-caused threats.

Buoyancy issues are harder to detect in young turtles as they naturally spend most of their time at the surface, whereas older turtles feed at the bottom, Zirkelbach explains. Much of the lightweight plastic also floats at the surface, where young turtles — less selective eaters than older turtles — might accidentally eat it. A 2020 study found plastic in the gastrointestinal tracts of more than 90 percent of the post-hatchling sea turtles examined.

Experts say buoyancy issues caused by plastic ingestion could be more common than currently known due to the difficulty in documenting this issue. “There’s a lot of turtles out there we never see,” says Zirkelbach.

“Plastic, unfortunately, doesn’t stay local and the impacts on hatchling turtles are likely to be high but unrecorded because they are far out to sea,” Menzies adds.

In Chex’s case, rescuers say it is difficult to definitively correlate his buoyancy issues to the balloon as they were also treating him with diet and medication at the time he passed the balloon.

“Determining the underlying cause of buoyancy can be challenging. Diagnostic imaging, such as radiographs and CT scans, is excellent for visualizing gas in the GI or an impaction or obstruction, but does not pick up all foreign material,” a Clearwater Marine Aquarium spokesperson said. “Metal shows up very clearly, but plastics and other soft materials can blend in with the tissues making diagnosis difficult.”

“Most of the time it is diagnosed when they pass pieces of plastic in their feces. Sometimes in larger turtles [it’s diagnosed] via endoscopy or surgery or if the turtle dies then on necropsy,” says Norton.

Rescued turtles face varying outcomes. Some turtles, like Chex, can pass the plastic and be released back into the wild. Others succumb to their injuries. The Turtle Hospital recently rescued a post-hatchling sea turtle with buoyancy issues. Once in their care, the turtle began showing positive signs: It was passing pieces of plastic and started eating again. But despite rescuers’ best efforts, the turtle passed away. A necropsy showed the turtle’s intestines and gut were filled with plastics.

Buoyancy caused by plastic ingestion may not be the most pressing threats to sea turtles, but it illustrates one of the many ways plastic can harm marine life.

Zirkelbach believes it’s important that people are hopeful when thinking about the impact of plastic debris on sea turtle: “I think we’re a smart species and we need to get on board with protecting our oceans and planet. [Reducing] single-use plastic is a big part of it.”

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