Microplastics are in the fetal tissues of Alaska spotted seals, new research finds

Yahoo

05-02-2025

A spotted seal pup is seen on the ice in the Bering Sea in 1978. New research confirms that pregnant spotted seals are transferring microplastics to their fetuses through the placentas. (Photo by Capt. Budd Christman/National Oceanic and Atmospheric Administration Corps)
Microplastics, tiny bits of plastic that can be too small to see with the naked eye, have infiltrated all environments around the world. From the Arctic to the Antarctic, they are found in water, snow, soil and the tissues of animals and people. In Alaska, they have been found in commercially important fish like pollock, in water bodies around the Southcentral region and in tap water in Anchorage.
Now there is more bad news about microplastics in Alaska: They are passed on from maternal spotted seals to their fetuses, according to research from the University of Alaska Fairbanks scientists.
A study that examined fetuses, amniotic fluid and placentas from eight pregnant spotted seals harvested between 2020 and 2023 by Indigenous subsistence hunters in the Bering Strait region turned up 1,415 bits, said Lara Horstmann, a UAF associate professor heading the project.
'Microplastics are definitely transferred over the placenta into the fetus,' Horstmann said in a presentation last week at the Alaska Marine Science Symposium in Anchorage.
Fetal livers contained the highest concentrations, five times that of fetal muscle, she found, but all samples except for two held some amount of microplastics, mostly fibers, she said.
Horstmann, who is with UAF's College of Fisheries and Ocean Sciences, leads a project that is studying microplastic levels in a variety of Alaska marine mammals. Students in the program, both at the graduate and undergraduate level, are pursuing their own studies of individual species.
For Horstmann's work with spotted seals, samples came from the Alaska Department of Fish and Game, which collects subsistence hunters' donation of seals' reproductive systems. The samples she tested also included fetal muscle and organs.
It adds to other information about microplastics in marine mammals swimming in Arctic waters that might be considered remote.
So far, along with spotted seals, the UAF team has examined walruses, belugas, bearded seals and northern fur seals.
'We've pretty much found microplastics now in every tissue that we've looked at, so muscle, blubber, liver, kidney, you name it,' Horstmann said in her presentation at the symposium.
Among her students, Chelsea Kovalcsik showed how microplastics are pervasive in northern fur seals at St. Paul Island in the Bering Sea. Among seals harvested by subsistence hunters in 2022 and 2023, concentration of microplastics in muscle tissue turned out to average 1.5 parts per gram and concentrations in blubber averaged 1.3 per gram, according to the findings.
Tony Blade followed up on previous work examining walrus samples from animals harvested by subsistence hunters; his study from last year was the first to document microplastics within tissues of walruses. His follow-up work found higher concentration of the plastic bits in walrus muscle than in walrus blubber and mixed results about the relationship between animal age and microplastic concentration.
Noelle Picard is tracking microplastic levels in beluga whales from the Arctic. Using samples collected by the North Slope Borough, she found the highest levels in livers, muscles, kidneys and blubber.
Linnaea Doerner is focused on bearded seals and trying to determine if there has been a trend over time in microplastic accumulation. So far, she found concentrations in those seals' muscle, liver and blubber tissues.
The species and results may differ, but there is a common theme, Kovalcsik said.
'There's varying numbers here, right? But it's ubiquitous. We're finding them in all tissues at varying amounts,' she said during her presentation at the symposium.
The UAF project grew out of Alexandra Sletten's work as a UAF graduate student tracking microplastics in stomachs of spotted seals harvested by subsistence hunters in the Bering Strait region. Her project found that 28 of the 29 stomachs she examined held microplastics.
Sletten now works for the Alaska Department of Fish and Game and was the department contact who supplied the samples that Horstmann used for her study of maternal transfer to fetuses.
The UAF group's work also builds on information from previous research that showed that microplastics ingested by a variety of marine mammals have become lodged in muscle, blubber and organs.
Results from a wide-ranging 2023 study led by Duke University scientist Greg Merrill showed that 'translocation' of microplastics – the movement through membranes – has occurred in a variety of whales, seals and dolphins in Alaska, California and North Carolina. Merrill presented his findings at last year's Alaska Marine Science Symposium.
The plastic bits in the animals' bodies pose myriad problems. If the mostly fibrous pieces match the makeup of what has been found by other scientists in Chukchi Sea sediments, they are dominated by materials like polyethylene and rayon, 'and that is not good news because both of those are are endocrine disruptors,' Horstmann said.
Endocrine disruptors are chemicals that interfere with the body's hormone system, affecting reproduction, immunity and other functions.
Other endocrine disruptors spread by microplastics are phthalates, chemicals that make plastics softer but are also considered toxins. Years of work by Veronica Padula as she earned degrees from both UAF and the University of Alaska Anchorage tracked levels of phthalates in Bering Sea birds.
There are also concerns that because of their absorption qualities, microplastics will help deliver algal toxins – which are increasing in presence in warming Arctic waters – into animals' bodies.
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Whether the presence of microplastics is affecting Alaska marine mammals has yet to be determined.
But Kovalcsik, for one, has her suspicions, at least about northern fur seals, which have been in steady decline since the 1950s.
'We have this decline in northern fur seals and is it due to a bunch of things? Most likely. But is it probably also due to microplastics? Sure,' she said.
The northern fur seal population totaled over 2 million in the mid-20th century but is now down to about 700,000, according to the National Oceanic and Atmospheric Administration. The decline is continuing.
Also yet to be determined is the exact source of the microplastics found in Arctic Alaska waters and marine mammals' bodies.
Much of it is believed to have been carried vast distances from southern latitudes.
In the same way that banned or restricted pollutants like DDT and polychlorinated biphenyls, or PCBs, have been transported north to the Arctic by air and ocean currents, tiny microplastics are also pulled north over thousands of miles. That has made the Arctic a sink for microplastics, just as it has been a sink for the chemical pollutants.
Some of that is explained by what is called the 'grasshopper effect.'
'Chemicals volatilize from places of production, use, and waste disposal, then move through the air toward the northern and southern polar regions on prevailing atmospheric currents. They re-deposit to the ground when they meet colder air masses, then remobilize to the air with warming temperatures—thus 'hopping' their way to the Arctic or Antarctic,' said a report released last year by Alaska Community Action on Toxics, a nonprofit organization.
Climate change is a factor as well, scientists say.
Microplastics locked over the past decades in sea ice are now being released as that ice melts. Those plastic bits are found even in the most remote parts of the Arctic. A 2020 study by an international team found over 2,000 pieces of microplastic in sea ice cores taken from the Central Arctic Ocean.
As more freshwater flows into the Arctic Ocean and as shipping activity increases in waters that are open for longer periods in the year, both results of Arctic climate change, more microplastics are expected to arrive in the far north, scientists say.
Microplastics, in turn, hasten the melting that is part of a feedback loop of accelerating Arctic warming. Microplastics darken white snow and ice, increasing the absorption of solar heat, which then exposes more dark surfaces that absorb solar heat, scientists say.
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