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As long as there is marine life, there is also sea snow – an endless drizzle of death and waste that sinks from the surface to the depths of the sea.

Snow starts out as granules that coalesce into dense, lumpy flakes that slowly sink to the bottom and are dragged further down past the scavengers’ mouths (and mouth-like devices). But even swallowed sea snow will likely be snowfall once again; A squid’s gut is just a resting stop on this long passage to the deep.

Although the term brings to mind winter whites, sea snow is mostly brownish or grayish and consists mostly of dead stuff. Through the ages, the debris contained the same things—speckles from plant and animal carcasses, feces, mucus, dust, microbes, viruses—and carried the ocean’s carbon to be stored on the seafloor. However, snowfall in the seas is increasingly filtered by microplastics: fibers and fragments of polyamide, polyethylene and polyethylene terephthalate. And this false fall seems to be changing our planet’s ancient cooling process.

Tens of millions of tons of plastic enter the Earth’s oceans each year. Scientists initially assumed that the material was destined to float in dumps and eddies, but surveys have only approximated it. one percent Estimated amount of plastic in the ocean. a new model to create 99.8 percent of the plastic that has entered the ocean since 1950 had sunk below the first few hundred feet of the ocean. Scientists have found 10,000 times There is more microplastic on the seafloor than contaminated surface waters.

Sea snow, one of the main pathways connecting surface and depth, seems to help the plastic sink. And scientists are just beginning to unravel how these materials interfere with deep-sea food webs and the ocean’s natural carbon cycles.

“It’s not just that the snow in the sea carries plastics or aggregates with plastic,” said Luisa Galgani, a researcher at Florida Atlantic University. “The fact that they can help each other to reach the deep ocean.”

making snow at sea

The sunny surface of the sea blooms with phytoplankton, zooplankton, algae, bacteria and other small creatures, all feeding on the sun’s rays or each other. As these microbes metabolize, some produce polysaccharides that can form a cell. sticky gel attracting the inanimate bodies of small organisms, small fragments of larger carcasses, shells from foraminifera and pteropods, sand and microplastics that stick together to form larger scales. Dr. “They’re the glue that holds all the components of sea snow together,” Galgani said.

Sea snowflakes fall at different rates. Smaller ones have a heavier descent — “as slow as a meter a day,” says Anela Choy, a biological oceanographer at the Scripps Institution of Oceanography at the University of California, San Diego. Larger particles, such as dense fecal pellets, may sink faster. “It’s launching all the way to the bottom of the ocean,” said Tracy Mincer, a researcher at Florida Atlantic University.

Plastic in the ocean is constantly breaking down; Even something as big and mobile as a milk jug will eventually turn into microplastics and break down. These plastics develop biofilms of different microbial communities—the “plastisphere,” said Linda Amaral-Zettler, a scientist with the Royal Netherlands Naval Research Institute, who coined the term. Dr. “We think the plastic is dormant,” Amaral-Zettler said. “Once it enters the environment, it is quickly colonized by microbes.”

Microplastics can harbor so many microbial hitchhikers that they defy the plastic’s natural buoyancy, causing their raft to sink. But if the biofilms degrade as they descend, the plastic can float back up, potentially leading to a yo-yoing microplastic purgatory in the water column. Sea snow is anything but stable; As free-falling flakes into the abyss, they constantly freeze and disperse, being torn apart by waves or predators.

“It’s not that simple: Everything is falling all the time,” said Adam Porter, a marine ecologist at the University of Exeter in England. “A black box in the middle of the ocean because we can’t stay there long enough to understand what’s going on.”

Dr. To discover how marine snow and plastics are dispersed in the water column, Mincer began sampling deeper waters with a pump filled with dishwasher-size filters, which swung on a wire from a research boat. The filters are arranged from large mesh to small to filter out fish and plankton. Running these pumps at a stretch for 10 hours revealed nylon fibers and other microplastics dispersed throughout the water column under the South Atlantic subtropical eddy.

But even with a research vessel and her expensive and cumbersome equipment, not a single piece of sea snow can be easily retrieved from the deep waters of a real ocean. Pumps often break up the snow and disperse the fecal pellets. And the flakes alone give little idea of ​​how quickly some snow is sinking; this is vital to understanding how long plastics linger, yo-yo or sink in the water column before settling on the seafloor.

“Decades of years?” Dr. Mincer asked. “Centuries? Then we can understand why we’re here and what kind of problem this really is.”

To answer these questions and work within a budget, some scientists have made and manipulated their own marine snow in the lab.

In Exeter, Dr. Porter collected buckets of seawater from a nearby estuary and loaded it into constantly rolling bottles. He then sprinkled microplastics, including polyethylene beads and polypropylene fibers. The constant agitation and the sticky gush of hyaluronic acid encouraged the particles to collide and stick together in the snow.

Dr. “Obviously we don’t have a 300-foot tube to submerge it,” Porter said. “What you’re doing by rolling is creating a never-ending column of water for particles to fall through.”

After the bottles had been rolled for three days, he piped the snow and analyzed the number of microplastics in each flake. His team found that every type of microplastic they tested collects in sea snow, and that microplastics like polypropylene and polyethylene – normally too buoyant to sink on their own – sink easily after mixing with sea snow. And all sea snow contaminated with microplastics sank significantly faster than natural sea snow.

Dr. Porter suggested that this potential change in snow velocity could have huge implications for how the ocean captures and stores carbon: Faster snowfalls can store more microplastics in the deep ocean, while slower snowfalls can make plastic-laden particles more available. predators, potentially starving deeper food webs. “Plastics are a diet pill for these animals,” said Karin Kvale, carbon cycle scientist at GNS Science in New Zealand.

Dr. In experiments in Crete, with funding from the European Union’s Horizon 2020 research program, Galgani tried to mimic sea snow on a larger scale. Six mesocosms—huge bags each containing about 800 gallons of seawater, recreating natural water movement—dropped into a large pool. Under these conditions, sea snow formed. Dr. “You’re observing more in the field,” Galgani said. “You have very little space and a limited system. You are manipulating a natural system in the mesocosm.”

Dr. Galgani mixed microplastics into three mesocosms in an attempt to “recreate a sea and perhaps a future ocean where you can have high concentrations of plastic.” Mesocosms filled with microplastics produced not only more marine snow, but also more organic carbon, because plastics offered more surface for microbes to colonize. All this could seed the deep ocean with even more carbon and change the ocean’s biological pump that helps regulate the climate.

Dr. “Of course, that’s a very, very big picture,” Galgani said. “But we have some signals that it may have an effect. Of course, it depends on how much plastic it is.”

A plastic feast

To understand how microplastics circulate in deep-sea food webs, some scientists turned to the creatures for clues.

Every 24 hours, many species of marine organisms begin a synchronized up and down migration in the water column. Dr. “They do the equivalent of a marathon every day and night,” Choy said. “Is it possible for them to move plastics up and down?” Guilherme VB Ferreira, a researcher at the Rural Federal University of Pernambuco in Brazil, asked. she wondered.

A PhD student at the same university, Dr. Ferreira and Anne Justino collected vampire inks and mid-water inks from part of the tropical Atlantic. They found copious amounts of plastic in both species: mostly fibres, but also pieces and beads.

This made sense for fish that directly eat microplastics at night, and mid-water squid that migrate to the surface to feed on copepods. But the vampire squid, which lived in deeper waters with less microplastic, had higher levels of plastic and foam in their stomachs. The researchers hypothesize that the vampire squids’ primary diet of sea snow, particularly the meatier excrement pellets, may leach plastic into their bellies.

“This is very worrying,” said Miss Justino. Dr. Ferreira said: “This is one of the most vulnerable species to anthropogenic impact.”

Ms. Justino extracted fibers and beads from the digestive tracts of anglerfish, hatchetfish, and other fish that migrated up and down 650 to 3300 feet in the mesopelagic. Dr. Some microbial communities that settle in microplastics may show bioluminescence, attracting fish like a bait, Mincer said.

At Monterey Bay Canyon, Dr. Choy wanted to understand whether certain types of filter feeders ingest microplastics and carry them into food webs in deeper waters. “Marine snow is one of the most important things that connects food webs across the ocean,” he said.

Dr. reset giant larva on Bathochordaeus stygius. The larva resembles a small tadpole and lives in a palace-like mucus bubble that can reach a meter long. Dr. “Worse than the biggest snot you’ve ever seen,” Choy said. When the slime burrows become clogged without feeding, the larvae pop out and the heavy bubbles sink. Dr. Choy discovered that these mucus palaces are filled with deep-flowing microplastics, along with all their carbon.

Giant larvae are found in the world’s oceans, but Dr. Choy emphasized that his work is focused on the Monterey Bay Canyon, which belongs to the network of marine protected areas and does not represent other, more polluted seas. Dr. “A deep cove on one coast of a country,” Choy said. “Large your scale and think about how vast the ocean is, especially the deep waters.”

Individual marine snow flakes are small, but they do add up. A model Dr. Created by Kvale, he estimates that in 2010 the world’s oceans produced 340 quadrillion marine snow, which could carry as many as 463,000 tons of microplastics to the seafloor each year.

Scientists are still investigating exactly how this plastic snow sank, but they know for sure, said Dr. Porter, “everything eventually sinks in the ocean.” Vampire squids will live and die and eventually become sea snow. But the microplastics that pass through will settle on the seafloor in a stratigraphic layer that will mark our time on the planet long after humans are gone.