Study: Microplastics Were in the Gut of Every Sea Turtle Tested

Every year, anywhere from 5 million to 12 million tons of plastic debris enter waterways worldwide, which equates to an estimated 5 trillion pieces of plastic.¹ While some of this plastic is in the form of large debris like plastic bottles, six-pack rings and bags, much of it is in the form of tiny particles known as microplastics, which are less than 5 millimeters (mm) in size.

Microplastics can come from direct or “primary” sources, such as microbeads used in cosmetics or fibers used in clothing. They can also be secondary microplastics, meaning they’re the result of larger plastic items that have disintegrated due to exposure to waves, salt water, ultraviolet radiation and physical abrasion against shorelines.

Microplastics do not, unfortunately, simply disappear into the water. Their prevalence and abundance has made them one of the worst polluters in the oceans, with a variety of marine life ingesting the particles, either by intention or happenstance.

Sea Turtles Are Ingesting Microplastics

Research published in Global Change Biology revealed that microplastics are ubiquitous in sea turtles.² Every turtle tested, which included 102 turtles from all seven marine turtle species from three ocean basins (Atlantic, Mediterranean and Pacific), contained the plastics, at varying levels.

Most abundant were plastic microfibers (most often blue or black in color), but fragments and microbeads were also detected, albeit in lesser quantities. Microfibers come from many sources, including shedding from synthetic fabrics, wear from automotive tires and degradation of cigarette filters and fishing nets and ropes.

Once in the water, turtles may be exposed via contaminated sea water and sediments. In the latter case, many sea turtles are known to feed along the ocean bottom, stirring up and ingesting sediment along with their prey.

They may also be exposed directly via their dietary sources. Microplastics can bind to seaweed electrostatically, for instance, while sponges, another turtle delicacy, also ingest microplastics.

In all, more than 800 particles were found by the researchers,³ but because the featured study only tested a small sample of the turtles’ gut content residue, it’s believed that their findings represent only minimum exposure levels to plastics.

“The total number of synthetic particles within the whole gut is likely to be the order of 20 times higher,” the researchers explained. “This suggests that the total levels of ingestion per individual (whole gut) may be higher in marine turtles than large marine mammals.”⁴

While microplastics don’t pose a risk of internal blockage the way larger plastics do, it’s likely that they affect marine animals on a more subtle, put potentially equally harmful, level. Microplastics may act like sponges for contaminants including heavy metals, persistent organic pollutants, polychlorinated biphenyls (PCBs) or pathogens, for instance, or could cause harm on a cellular or subcellular level, the study noted.

Sea Turtle Hatchlings Threatened by Microplastics

While the Global Change Biology study authors did not believe microplastics would pose as grave a risk to sea turtles as ingestion of larger plastic debris, this may not be the case for post-hatchling sea turtles.

“They’re pretty nondiscriminatory with what they’re eating at this life stage. They eat whatever floats past them,” Samantha Clark, a veterinary technician at the Loggerhead Marinelife Center (LMC) in Juno Beach, Florida, said in a news release.⁵ Clark cowrote a study that involved 96 post-hatchling sea turtles collected from the Atlantic coastline in Florida.⁶

Forty-five of the turtles were able to be rehabilitated and released, but 52 of the turtles died, allowing the researchers to analyze their gastrointestinal tracts, most of which contained visible pieces of plastic. Microplastics, larger mesoparticle plastics and even smaller nanoparticles were found in the turtles, with polyethylene and polypropylene the most common types of plastic detected.

“[I]ngestion of micronizing plastic by post-hatchling sea turtles is likely a substantial risk to survival of these endangered and threatened species,” the study concluded, with study coauthor Dr. Charles Manire, director of research and rehabilitation at LMC, adding, “It’s not a question of if they have it, it’s how much they have.”

He told global conservation news service Mongabay, “Twenty-five years ago we would occasionally see a little bit of plastic in some of the smallest turtles,” said Manire. “Now, essentially, 100 percent of them have it … Sea turtles tell us the health of the ocean. The ocean tells us the health of the planet.”⁷

Filter Feeders Also at Risk

Other marine life, including filter-feeding sharks, rays and baleen whales, are also being negatively affected by microplastics. Animals like these may swallow thousands of cubic meters of water daily in order to capture enough plankton to survive, and with it they’re exposed to whatever else may be lurking in the water.

Not only do filter feeders live in some of the most polluted waters on the planet, but their numbers are already threatened. Half of the species of mobulid rays, along with two-thirds of filter-feeding shark species and more than one-quarter of baleen whale species are listed as threatened species by the International Union for the Conservation of Nature (IUCN).⁸

“Emerging research on these flagship species highlights potential exposure to microplastic contamination and plastic-associated toxins,” according to a study in Trends in Ecology & Evolution.⁹ Study author Elitza Germanov, researcher at the Marine Megafauna Foundation, told Phys.org:¹⁰

“Despite the growing research on microplastics in the marine environment, there are only few studies that examine the effects on large filter feeders. We are still trying to understand the magnitude of the issue.

It has become clear though that microplastic contamination has the potential to further reduce the population numbers of these species, many of which are long-lived and have few offspring throughout their lives."

Are You Eating ‘Plastic’ Fish?

The Center for Biological Diversity noted that fish in the North Pacific are known to ingest 12,000 to 24,000 tons of plastic every year, and, in a study of fish markets in California and Indonesia, one-quarter of the fish were found to have plastics in their guts.¹¹

Plastics and other man-made debris was also found in 33 percent of shellfish sampled.¹² What this means is that when you sit down to a seafood dinner, you’re probably eating plastic.

Writing in the journal Integrated Environmental Assessment and Management, researchers noted, “The potential for humans, as top predators, to consume microplastics as contaminants in seafood is very real, and its implications for health need to be considered.”¹³

The fact is, fish aren’t eating microplastic only by mistake. The particles develop a biological covering of algae and other organic materials while they’re floating in the ocean. And that film makes them smell like food to marine life.

Anchovies, for instance, use odors to forage, and the smell of microplastic entices the fish to eat. Study author Matthew Savoca, of the National Oceanic and Atmospheric Administration, told the Guardian:¹⁴

“When plastic floats at sea its surface gets colonized by algae within days or weeks, a process known as biofouling. Previous research has shown that this algae produces and emits DMS, an algal based compound that certain marine animals use to find food.

[The research shows] plastic may be more deceptive to fish than previously thought. If plastic both looks and smells like food, it is more difficult for animals like fish to distinguish it as not food.”

There’s Probably Plastic in Your Sea Salt and Bottled Water, Too

Microplastics, including microfibers, are seemingly everywhere. For instance, they were also found to be the predominant type of microplastic found in beer, tap water and sea salt samples.

“Based on consumer guidelines, our results indicate the average person ingests over 5,800 particles of synthetic debris from these three sources annually, with the largest contribution coming from tap water (88 percent),” according to researchers in PLOS One.¹⁵

Another study revealed the average person may swallow an estimated 68,415 plastic fibers every year just from contaminated dust landing on their plate during meals.¹⁶ This is a much larger source of exposure than plastics from seafood such as shellfish, those researchers noted, stating, “The risk of plastic ingestion via mussel consumption is minimal when compared to fiber exposure during a meal via dust fallout in a household.”¹⁷

Other sources of microplastics that you probably come across daily include sea salt, as 90 percent of sea salt sold worldwide contains plastic microparticles; it’s estimated that people consume nearly 2,000 such particles a year in their sea salt alone.¹⁸ More than 90 percent of popular bottled water brands sampled also contained microplastics, which in some cases may be coming from the packaging and bottling process itself.¹⁹

That being said, 94 percent of U.S. tap water samples were also found to contain plastic,²⁰ with microfibers again representing a major part of the problem. Even sewage sludge, which is applied as a fertilizer in industrial agriculture, is loaded with microfibers,²¹ which were found to cause changes in the soil, including altering the bulk density, water-holding capacity and microbial activity.

Are You Part of the Problem or Part of the Solution?

The magnitude of plastic used worldwide daily is mind-boggling, but you can make a dent by becoming conscious of the plastic you’re using daily — and cut back where you can. Some steps are easy, like swapping plastic bags, bottles, straws, utensils and food containers for more durable, reusable options.

Other steps may take more thought, like reconsidering what types of clothes to buy. A synthetic jacket (such as a fleece) may release up to 2.7 grams (0.095 ounces) of microfibers with each washing (that’s up to 250,000 microfibers). On average, such a garment releases 1.7 grams of microfibers, although older jackets released fibers at twice the rate.²²

So one thing you can do to curb plastics pollution is to wash your fleece and microfiber clothing less often, and when you do use a gentle cycle to reduce the number of fibers released. There are also products on the market that catch laundry fibers in your washing machine to help curb pollution.

Special coatings may also help to stop the loss of microfibers during washing, but the apparel industry has been slow to respond in taking steps to stop microfiber pollution.²³ You can also consider what your clothing is made out of. In a comparison of acrylic, polyester and a polyester-cotton blend, acrylic was the worst, shedding microfibers up to four times faster than the polyester-cotton blend.²⁴

Ultimately, however, plastic pollution needs to be curbed at its source. Rivers, being a major source of transport of plastic into oceans, should be a major focus of cleanup and prevention efforts. In fact, 95 percent of the riverborne plastic flowing into the ocean comes from just 10 rivers.²⁵

Martin Wagner, an associate professor at the Norwegian University of Science and Technology’s (NTNU) department of biology, believes that focusing on removing plastic from the ocean is a shortsighted solution because in order to stop it in the long run, it has to be traced back to its source, which in most cases is land and the rivers that transport it.²⁶

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