Why Is the Ocean Snowing Microplastics?


Do you ever wonder where the plastics go that you use?


Did you know the ocean snows, but not the snow you and I are familiar with…


The ocean snows with marine life, which is where the term ‘marine snow’ comes from. Marine snow is a shower of organic material (mostly biological debris) that falls from the top layers of the ocean, drifting down to the deep and eventually, the seafloor.


Marine snow gradually sinks to scavengers that devour the organic matter. When we think of snow, we think of fluffy white flakes, but marine snow is mostly brownish or greyish because of the composition: plant and animal carcasses, faeces, mucus, dust, microbes, and viruses.


Unfortunately, humans are destroying this natural process, and now marine snowfall is being infiltrated by microplastics. These microplastics include fibres and fragments of polyamide, polyethylene, and polyethylene terephthalate. According to scientists, these microplastics seem to be altering our planet’s ancient cooling process, which is very worrying.


Every year, it is estimated that 8 million metric tons of plastics enter Earth’s oceans, on top of the 150 million metric tons that are already circulating in our marine environments. Scientists used to believe that the plastic material would float in large garbage patches and gyres, like the Great Pacific Garbage Patch, however, surface studies tell us a different story…


Floating plastics in the ocean only account for 1% of the total amount of ocean plastic, so where does the other 99% go?


You guessed it, it sinks below the ocean’s surface. Since 1950, 99.8% of the plastic that has entered our oceans has sunk below the first few hundred feet, which has led scientists to find 10,000 times more microplastics on the seafloor than in surface waters.


But, the bad news doesn’t stop there…


Marine snow appears to be helping the microplastics sink, leading scientists to investigate how plastics are interfering with the deep-sea food web and the ocean’s natural carbon cycles.


Luisa Galgani, a marine researcher at Florida Atlantic University, has said: “It’s not just that marine snow transports plastics or aggregates with plastic, it’s that they can help each other get to the deep ocean.”


Before we go into why snowing microplastics is an issue, you need to understand how marine snow is naturally made.


 

How Is Marine Snow Formed?


The ocean’s surface waters are rich with phytoplankton, zooplankton, algae, bacteria, and other tiny critters that require sunlight for nutrition.


Once these microbes metabolise, some form a sticky gel when they produce polysaccharides. This sticky gel attracts dead organisms and worryingly now microplastics, to form larger flakes of marine snow.


Similar to snow on land, marine snowflakes fall at different rates depending on the size; smaller flakes of marine snow will have a slower descent rate than larger flakes.


OK, so now back to the microplastic issue…


When plastics enter the ocean, they are constantly degraded, breaking down into smaller plastics, which we refer to as microplastics (fragments of any type of plastic less than 5 mm (0.20 in) in length). Once plastics enter the ocean, they are rapidly colonised by microbes, allowing microbial hitchhikers to grab a ride to the deeper depths of the ocean.


Sometimes, the plastics do not make it all the way down. If the biofilms were to degrade on the way down to the seafloor, the plastic can float back up, as there are no microbes to weigh it down. This causes the constant yo-yo-ing of microplastics in the water column, where many filter-feeding organisms live, unintentionally ingesting the microplastics.


The problem scientists have is the difficulty to study the deeper ocean for long periods. Adam Porter, a leading marine ecologist from the University of Exeter in England, states: “It’s a black box in the middle of the ocean, because we can’t stay down there long enough to work out what’s going on.”


To understand marine snow and the impact of microplastics, Dr. Tracy Mincer, a research professor from the FAU Harbor Branch Oceanographic Institute, has started to sample microplastic in deeper waters below the South Atlantic subtropical gyre.


Her ongoing research hopes to find what the problem really is, but so far she says “Deep-sea fishes at one thousand meters have been found to have plastics in them,” therefore, “Plastic debris is affecting fisheries and food security”. This is a serious impact, as it not only affects marine life, but microplastics are also entering the human food chain.


Because studying the effect microplastics have in deeper water poses a challenge, some scientists are studying marine snow in a lab.


Let’s take a look at what they found!


 

Lab Studies: The Impact of Snowing Microplastics!


Dr. Porter from Exter collected buckets of seawater from a nearby estuary and placed them into continuously rolling bottles to create the ocean’s natural water movement.


Next, he scattered microplastics including polyethylene beads and polypropylene fibres that we know enter our oceans. The turning of the bottles and adding sticky hyaluronic acid stimulated particles to stick together.


He is well aware that in a lab there are not 300 metres of water to make the snow sink, however, he says “by rolling it, what you’re doing is you’re creating a never-ending water column for the particles to fall through.”


After 3 days, he used a pipette to remove the snow and counted the number of microplastics bound to each snowflake. His team anxiously found microplastics in each flake, and the plastics that contained polypropylene and polyethylene which usually are too buoyant to sink on their own, sank significantly faster when they bound to the natural marine snow.


So, why is that an issue?


Well, Dr. Porter suggested that the potential change in sinking rates could have great implications for how the ocean captures and stores carbon.


This hypothesis is backed by Dr. Galgani who also mixed microplastics with seawater in a lab. She found that not only did microplastics produce more marine snow, but they also increased the amount of organic carbon in the seawater because the plastics offer more surfaces for microbes to colonise.


If what happened in Dr. Galgani’s lab is what is going on in our oceans, it is not good news!


If her lab studies are a mirror image of what is going on in our oceans, she says the sinking of microplastics is likely to increase the amount of carbon which will alter the ocean’s biological pump, which helps regulate Earth’s climate.


She recognises the unknown because of the current lack of deep-sea research, and that “Of course, it’s a very, very big picture,” but she continues to say that “we have some signals that it can have an effect. Of course, it depends on how much plastic there is.”


As you know, the ocean is teeming with marine life, so, to understand how microplastics travel through the deep-sea food web, scientists are now turning to marine creatures for some answers.


 

Are Microplastics Becoming An Underwater Feasting Frenzy?


Every day, marine organisms take off on a synchronised journey up and down the ocean’s water column. To put it into perspective, they travel the equivalent of a marathon every 24 hours!


As we know microplastics are accumulating in our oceans and binding to marine organisms, it is highly likely they are joining in on this journey and being eaten by larger marine creatures.


We know this because Dr. Ferreira collected midwater and vampire squids from the tropical Atlantic and found an excessive amount of plastics in both species. The plastics found mostly consisted of fibres, but also plastic beads and fragments were found.


He says that it made sense for the midwater squids to contain microplastics, as they migrate towards the surface during the night to feed on fish and copepods that likely directly ingest microplastics.


But it was vampire squids that concerned him because they live in deeper waters. Not only did the vampire squids have a greater number of microplastics inside their stomach, but polyethylene foam was also found.


Because of the findings, Dr. Ferreira believes that vampire squids primarily eat marine snow which may be funnelling the microplastics into their stomachs. This is very concerning as “They are one of the most vulnerable species for this anthropogenic influence.” says Dr. Ferreira.


As some microbial communities that hitchhike on microplastics can bioluminescence, they lure fish to consume the plastics.


 

How Deep Can Microplastics Travel In the Ocean?


This is difficult because of the lack of current research, however, plastic fibres and beads have been found in the digestive tract of lanternfish, hatchetfish, and other fish that regularly migrate up and down in the mesopelagic regions of the ocean.


Therefore, we know that microplastics fall to at least 3,300 feet (1006 m)!


 

How Many Microplastics & Marine Snow Particles Are Estimated To Reach the Seafloor?


Dr. Kvale from GNS Science created a model in 2010 that estimated 340 quadrillion particles of marine snow can actively transport as many as 463,000 tons of microplastic to the seafloor, EVERY YEAR!


Scientists are still exploring how microplastics are sinking the marine snow and the impacts it has on both marine life and creatures on land.


But, what they do know is that microplastics will continue to sink, eventually settling on the seafloor that will remain in our oceans long after humans are gone.


So, what can YOU do to help?


 

10 Ways to Limit Your Microplastics Intake & Impact


  1. Buy a water filter, and stop using bottled water (if possible).

  2. Buy non-synthetic eco-friendly swimwear and clothes.

  3. Change your laundry routine - install a fibre-catching filter, use a laundry ball and air dry your clothes.

  4. Let your hair air dry, don't use the dryer.

  5. Use public transport.

  6. Reduce your meat and fish consumption.

  7. Use plastic-free cosmetics and microbead-free beauty products.

  8. Use eco-friendly cleaning products around the home.

  9. Replace teabags with loose leaf tea.

  10. Support policies that aim to limit single-use plastics.



 



Written by Darby Bonner



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