New research from the University of Alaska Fairbanks found microplastics in nearly all of the spotted seals' stomachs examined in a recent study, published in the current issue of the peer-reviewed Marine Pollution Bulletin.
Plastic is the most common form of marine debris, making up about 80% of ocean pollution, according to the United Nations. As things like water bottles and fishing gear degrade over time, they break down into increasingly smaller pieces.
Microplastics — synthetic particles less than five millimeters in size — are often shed from consumer plastics, synthetic clothing or fishing gear. Pollution from microplastics has drawn increased attention in recent years. Studies have linked microplastics to cancers, hormone disruption and fetal development.
Biologist Alex Sletten, who led the UAF study, said the findings show how even remote regions aren't immune from human activity.
"When you think about the Arctic, you think about this pristine environment that hasn't really been touched by anthropogenic stress," she said. "In reality, there's so much microplastics out there."
"It blew my mind," she added.
The study is part of a growing body of work showing that even in far-flung parts of the Arctic, plastic pollution is deeply embedded in the ecosystem.
Sletten analyzed the stomachs of 34 spotted seals harvested from the Bering and Chukchi seas. She found microplastics in all but one.
Her research is the first study to document microplastic ingestion in marine mammals from the region, and it suggests the problem has been around for at least a decade. The seals were harvested in 2012 and 2020, and contamination levels didn't change much between those years.
Sletten's team used enzymes to break down fish and prey in the seals' stomachs, and then isolate the plastic particles. Sletten said the results didn't vary between the seals' ages, location or harvest year, which she says demonstrates how pervasive microplastics are.
The study also found evidence suggesting that the plastics may be bioaccumulating through the food web. That means species that are higher up the food chain likely ingest more microplastics because they feed on animals that also have microplastics in their systems.
Spotted seals feed largely on animals that live along the seafloor as well as on fish species that are relatively high up the food chain. Sletten's team found the levels in the seals were higher than that of their prey.
"What we found was that seals that were eating primarily prey from higher up the food chain had a tendency to have a higher microplastic abundance within their stomach," she said.
That has implications for people, too. The seals for the study were harvested in Gambell and Shishmaref, where communities rely on marine mammals for subsistence.
Sletten said understanding where microplastics are present in the environment can help people understand the risks when harvesting animals from that habitat, and that the team shared its findings with those communities.
"We know that microplastics are settling into the sediments of the Chukchi Sea, based on numerous survey research that's gone on there," Sletten said. "Being able to know what hazards are present enables you to come up with solutions and be part of that systemic change to improve your ecosystem that you're living in."
While this study focused only on stomach contents, related research has found microplastics in muscle tissue, internal organs and in the fetuses of pregnant seals.
"They're getting that exposure before they're even born, which is just wild," Sletten said.
