How will microplastics in the oceans affect marine life

As long as there has been marine life, there has been marine snow – a constant mist of death and waste sinking from the surface to the depths of the sea.

Snow begins as atoms, which gather into dense, compressed flakes that gradually fall and drift through the mouths (and mouth-like organs) of scavengers down. But even sea ice that devours is likely to fall again; Squid guts are just a stop to rest on this long passage to the rear.

Although the term may refer to winter whites, sea snow is often brown or gray, and consists mostly of dead matter. Over eons, the wreck contained the same things — patches of animal and plant carcasses, feces, mucus, dust, microbes, viruses — and transported carbon into the ocean to be stored on the sea floor. However, snowfall in the seas is increasingly infiltrated by microplastics: fibers and fragments of polyamide, polyethylene and polyethylene terephthalate. This false error appears to be altering the ancient cooling process of our planet.

Each year, tens of millions of tons of plastic enter Earth’s oceans. Scientists initially assumed the material was to float in garbage patches and eddies, but surface surveys only accounted for about one percent of the estimated ocean plastic. A recent model found that 99.8 percent of the plastic that has entered the ocean since 1950 has sunk under the first hundreds of feet of ocean. Scientists have found 10,000 times more microplastics on the sea floor than in polluted surface waters.

Marine snow, one of the primary pathways connecting the surface to depth, appears to help the plastics sink. Scientists are just beginning to solve the mystery of how these materials interfere with deep-sea food webs and the ocean’s natural carbon cycles.

“It’s not just marine snow for plastic or agglomerate for plastic,” said Louisa Galgani, a researcher at Florida Atlantic University. “It’s about their ability to help each other reach the depths of the ocean.”

The sunlit surface of the sea thrives on phytoplankton, zooplankton, algae, bacteria and other tiny organisms, all of which feed on sunlight or one another. During the metabolism of these microbes, some of them produce polysaccharides that can form a viscous gel that attracts the dead bodies of the microorganisms, small pieces of larger bodies, the shells of foraminifera and pteropods, sand and microplastic particles, which stick together to form larger flakes. “It’s the adhesive that holds all the components of the sea ice together,” said Dr. Galgani.

Marine snowflakes fall at different rates. Smaller ones have much weaker proportions — “as slow as a meter per day,” said Anila Choi, a biological oceanographer at the Scripps Institution of Oceanography at the University of California, San Diego. Larger particles, such as dense fecal pellets, can sink faster. “It’s going up to the ocean floor,” said Tracy Mincer, a researcher at Florida Atlantic University.

Plastic in the ocean is constantly degrading; Even something as large as a milk jug will eventually flake and crack into microplastics. These plastics develop biofilms for distinct microbial communities – the “plastic ball,” said Linda Amaral Zeitler, a scientist at the Royal Netherlands Institute for Marine Research who coined the term. “We kind of think of plastic as inert,” Dr. Amaral-Zetler said. “Once it enters the environment, microbes quickly colonize it.”

Microplastics can host so many wandering microbes that they resist the natural buoyancy of the plastic, causing their raft to sink. But if the biofilms deteriorate on their way down, the plastic may float back up, potentially resulting in a microplastic sanitizer in the water column. Sea ice is not stable; When flakes fall into the abyss, they constantly freeze and disintegrate, cracking with waves or predators.

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

To investigate how marine ice and plastic are distributed in the water column, Dr. Mincer began sampling deep-water using a dishwasher-sized pump filled with filters that hang on a wire from a research boat. Filters are arranged from large to small mesh to filter fish and plankton. Running these pumps for 10 hours along the way revealed the presence of nylon fibers and other microplastics distributed throughout the water column below the subtropical circulation in the South Atlantic.

But even with the search boat and its expensive and impractical equipment, an individual piece of sea ice cannot be easily retrieved from the deep waters of the actual ocean. Pumps often disturb the ice and disperse fecal pellets. The chips alone provide little insight into how quickly some of the snow sinks, which is vital to understanding how long the plastic yo-yo remains or sinks into the water column before settling to the sea floor.

Are they contracts? asked Dr. Mincer. “Is it hundreds of years? Then we can understand what we are here for, and what kind of problem this really is.”

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

At Exeter, Dr. Porter buckets of seawater from a nearby estuary and carried water in circular bottles constantly. Then he sprayed microplastics, including polyethylene beads and polypropylene fibres. Constant stirring and a sticky hyaluronic acid mist encouraged the particles to collide and stick together in the snow.

“Obviously we don’t have 300m of tube to make it sink,” Dr. Porter said. “By rolling it, what you’re doing is creating an endless column of water for the particles to fall into.”

After the bottles had been rolling for three days, he sprinkled snow and analyzed the number of plastic particles in each shell. His team found that every type of microplastic they tested collects in sea ice, and that microplastics such as polypropylene and polyethylene — which are usually too buoyant to sink on their own — sink easily once they are incorporated into sea ice. And all marine snow contaminated with plastic particles sank much faster than natural marine snow.

Dr. Porter suggested that this potential change in the speed of snow could have major implications for how the ocean captures and stores carbon: Faster snowfall can store more microplastics in the ocean depths, while slower snowfall can make Plastic laden particles are more available. For predators, which are likely to starve the food webs in their depths. “Plastic is a food grain for these animals,” said Karen Kaval, a carbon cycle scientist at GNS Science in New Zealand.

In experiments conducted on the island of Crete, funded by the European Union’s Horizon 2020 research programme, Dr. Galgani attempted to mimic sea ice on a larger scale. Six medium worlds – huge bags each containing nearly 800 gallons of seawater and recreating natural water movement – were dropped into a large pond. Under these conditions, marine snow formed. “In the field, you mostly make observations,” Dr. Galgani said. “You have very little space and a limited system. In the intermediate world, you are manipulating a natural system.”

Dr. Galgani mixed microplastics in three medium worlds in an effort to “recreate a sea and possibly a future ocean where you could have a high concentration of plastic,” she said. Intermediate worlds filled with microplastics not only produced more marine snow, but also more organic carbon, as plastics provided more surfaces for microbial colonization. All of this could grow the ocean depths with more carbon and alter the ocean’s biological pump, helping to regulate climate.

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

To understand how microplastics can travel through deep-sea food webs, some scientists have turned to the creatures for clues.

Every 24 hours, many species of marine organisms embark on a simultaneous migration up and down the water column. “They do the equivalent of a marathon every day and night,” Dr. Choi said. Is it possible that they are moving plastics up and down?” asked Guilherme V. P. Ferreira, a researcher at the Federal Rural University of Pernambuco in Brazil.

Dr. Ferreira and Anne Justino, a doctoral student at the same university, collected vampire squid and squid in the middle waters of a patch of the tropical Atlantic. They found a large number of plastics in both types: mostly fibers, but also splinters and beads.

This made sense for middle-water squid, which migrate towards the surface at night to feed on fish and copepods that eat microplastics directly. But vampire squids, which live in deeper waters with fewer microplastics, had higher levels of plastic, as well as foam, in their stomachs. The researchers hypothesize that the sea ice’s vampire squid’s primary diet, especially the meatier fecal pellets, may be diversion of plastic into their stomachs.

“It’s very concerning,” said Ms. Justino. “It is one of the species most susceptible to this anthropogenic influence,” said Dr. Ferreira.

Ms. Justino excavated fibers and beads from the digestive tracts of lanternfish, baltic fish and other fish that migrate up and down the middle seas, at depths of 650 to 3,300 feet. Dr. Mincer said that some microbial communities that settle on microplastics can bioluminescent, attracting fish like bait.

In the Monterey Bay Valley, Dr. Choi wanted to understand whether certain types of filter feeders ingest microplastic particles and transfer them to deep-water food webs. “Sea ice is one of the main things that connect food webs across the ocean,” she said.

Dr. Choi focused on the giant caterpillars Bathochordaeus stygius. The larva looks like a small tadpole and lives inside a mucous bubble that can reach a meter in length. “It’s worse than the deadliest mucus I’ve ever seen,” Dr. Choi said. When their mucous homes become clogged with feeding, the larvae move out and sink into the heavy bubbles. Dr. Choi found that these mucus palaces are jammed with microplastics, which are channeled into the depths with all the carbon.

Giant grubs are found across the world’s oceans, but Dr. Choi emphasized that her work focused on the Monterey Bay Valley, which belongs to a network of marine protected areas and is not representative of other, more polluted seas. “It’s a deep bay on the coast of one country,” Dr. Choi said. “Expand and think about how wide the ocean, especially the deep waters, is.”

The individual flakes of sea snow are small, but they do pile up. A model devised by Dr. Keval estimated that in 2010, the world’s oceans produced 340 quadrillion masses of sea ice, which can transport up to 463,000 tons of microplastics to the sea floor each year.

Scientists are still figuring out exactly how this plastic ice sank, but they know for sure, as Dr. Porter said, that “everything eventually sinks into the ocean.” The vampire squid will live and die and eventually turn into sea ice. But the microplastics that pass through them will remain, eventually settling to the sea floor in a stratigraphic layer that will define our time on the planet long after humans are gone.

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