Guest essay by Eric Worrall
Scientists have discovered Antarctic Krill can digest or at least break up lumps of plastic into even smaller lumps – but when the krill were force fed large quantities of radioactive plastic over an extended period their ability to digest plastic deteriorated.
Krill found to break down microplastics – but it won’t save the oceans
Digestion of plastic into much smaller fragments ‘doesn’t necessarily help pollution’, Australian researchers say
A world-first study by Australian researchers has found that krill can digest certain forms of microplastic into smaller – but no less pervasive – fragments.
The study, published in Nature Communications journal on Friday, found that Antarctic krill, Euphausia superba, can break down 31.5 micron polyethylene balls into fragments less than one micron in diameter.
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Unfortunately, Dawson said, krill were unlikely to provide a solution to the levels of plastics and microplastics polluting the oceans.
“It’s not necessarily helping plastic pollution, it’s just changing it to make it easier for small animals to eat it,” she said. “It could be a new source of plastics for the deep ocean.”
A study by Newcastle University in December found microplastics in the stomachs of deep-sea creatures from 11km deep trenches in the Pacific Ocean.
Dawson said microplastics that had been digested by krill were also too small to be detected in most oceanic plastic surveys, meaning the level of microplastics in the ocean could be higher than currently assumed.
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The abstract of the study;
Turning microplastics into nanoplastics through digestive fragmentation by Antarctic krill
Amanda L. Dawson, So Kawaguchi, Catherine K. King, Kathy A. Townsend, Robert King, Wilhelmina M. Huston & Susan M. Bengtson Nash
Microplastics (plastics <5 mm diameter) are at the forefront of current environmental pollution research, however, little is known about the degradation of microplastics through ingestion. Here, by exposing Antarctic krill (Euphausia superba) to microplastics under acute static renewal conditions, we present evidence of physical size alteration of microplastics ingested by a planktonic crustacean. Ingested microplastics (31.5 µm) are fragmented into pieces less than 1 µm in diameter. Previous feeding studies have shown spherical microplastics either; pass unaffected through an organism and are excreted, or are sufficiently small for translocation to occur. We identify a new pathway; microplastics are fragmented into sizes small enough to cross physical barriers, or are egested as a mixture of triturated particles. These findings suggest that current laboratory-based feeding studies may be oversimplifying interactions between zooplankton and microplastics but also introduces a new role of Antarctic krill, and potentially other species, in the biogeochemical cycling and fate of plastic.
Read more: https://www.nature.com/articles/s41467-018-03465-9
The expression of concern about nano-plastic seems a stretch. Breaking micro-plastic into smaller chunks, making it available to even more versatile and varied microorganisms further down the food chain, is likely enough to effect complete clearance. Anyone who has ever owned a boat knows how difficult it is to protect fuel from contamination by the ubiquitous fungus and bacteria which thrives in sea water. It seems highly likely that at least one other organism, somewhere in the world’s oceans, has developed a taste for our plastic waste.
Correction (EW): the plastic wasn’t radioactive, I misread “Triturated” as “Tritiated” (h/t Phil)
Hmm, does that aid the bacteria that can ‘digest’ plastic/oil?
I believe it was George Carlin who said that the Earth wants plastic for itself. It’s incorporated into a paradigm: the Earth plus plastic.
(Yes, I have watched that video at least 3 dozen times. Well, 3.5. Okay, it was really 4.25 times.)
Isn’t evolution wonderful.
Plastic. Long chain, reasonably stable, and tough hydrocarbon compounds. Considering the rate at which evolution happens in smaller organisms, there are probably several out there that actually use the stuff for their structural elements.
krill were force fed large quantities of radioactive plastic
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what next. mutant killer krill.
better to force feed the researchers large quantities of radioactive plastic and see if this affects their appetite.
Damn nature always gets in the way.
Hmmm….. I wonder if the reduction in plastic particle size is simple mechanical reduction via the equivalent of krill mastication… or is it from a bacteria in their diminutive digestive tract?
From the paper–
“ Despite the properties of pristine polymers, all plastics, even those with chemical stabilisers, will eventually degrade in the environment.”
“ Of the 165 images taken, 2 images were excluded on the basis of chitinous material ….”
This suggested to me that a control using other more commonly encountered undigestible similarly size particles would be interesting. Krill live in clear water but there are always floating materials around, but such controls might still be inadequate.
From abstract of one of the citations on mussels, which might be bettered expected to be able to handle small particles.–“ The short-term pulse exposure used here did not result in significant biological effects.” Similar results for oyster larvae in another cited article– “ In conclusion, while micro- and nanoplastics were readily ingested by oyster larvae, exposure to plastic concentrations exceeding those observed in the marine environment resulted in no measurable effects on the development or feeding capacity of the larvae over the duration of the study.” Oysters do well, even better, in cruddy looking water so their tolerance is not unusual.
There was legitimate toxicological concern that manufactured hydrocarbons might be a bigger problem than those naturally occurring. Did it take a long time to get around to studying these and then based on amounts (cosmetics)?. Is the chemical nature of the colloidal sizes accurately known?
No surprise. There is an enormous amount of oil naturally seeping into the ocean every second. There is whole ecosystem that feeds on it. Same for methane and other natural gas. On land tar pits exist in California, Trinidad, Canada and many places. Just face it – oil is just composted critters from a long time ago – not so different from your garden compost heap except many many more years old, buried and baked from natural thermal heat and under pressure from sediment weight.
Oil is Mother Nature’s Fuel – the suns energy trapped by plants and the critters that eat them.
In this case the species being studied (krill) were more intelligent than the researchers – by a very long shot.
https://www.amazon.com/Mutant-59-Plastic-Eaters-Kit-Pedler/dp/0670496626/ref=nodl_
I read this as a teenager. Had forgotten about it until now.
” … but when the krill were force fed large quantities of radioactive plastic over an extended period their ability to digest plastic deteriorated. … ”
Well fancy that. Fussy little critters.
One wonders what they were thinking.
Biologists are great.
In nano sizes, it’s almost certain to be completely biodegradable. Plastics of all kinds become brittle and break up by weathering. The fact the fine pieces are spheres is evidence of “wear” by abrasion and chemical diminution. If plastic bottles and other forms are quickly reduced to millimetric particles, then sub-millimetre sizes and then taken in by krill at 30 microns and passes at 1 micron, why would the reduction stop. A highschool chemistry student knows (used to know?) that reduction in grain size greatly increases exposed area of a material which increases its vulnerability to chemical attack. Hey, the stuff is hydrocarbon based which is carbohydrates to biota in fine particles. Take it from a mining engineer!
Also an experiment must be conducted to do a proper mass balance of the degradation. Examining size reduction from injestion is not quantitative of the process. If one can keep krill alive and add in a measured weight of -30 micron plastic into the tank, then in time one can measure what remains. It’s trivial to expect the mass to reduce. A good scientific test but, sorry, you’ll have to go to a different publication than the guardian to get it published.
” … meaning the level of microplastics in the ocean could be higher than currently assumed. …”
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Well, if the quantity of plastic is “currently assumed”, then you could with equal credibility and validity ‘quantitatively’ “assume” something else to be true, or at least a useful alternative reality.
This is easy.
In the pacific high all the barneculs stick to everything and sink everything over time. Ed bray on the schooner de Viento.
…Correction (EW): the plastic wasn’t radioactive, I misread “Triturated” as “Tritiated” (h/t Phil)…
I’d be surprised if it didn’t have some level of radioactivity – pretty much everything emits residual levels of radiation. Which must be a gift for any activist: “You are letting your children play with toys made from Scary radioactive plastic..!!!”
I wonder what levels of radiation you get from home-grown broccoli?
And there are bacteria that digest the black blob. The “green” blight, including windmills and photovoltaic panels, not so much.
Their next hysterical slogan will be, “Krill Kills!”.
What is the state of ‘old plastic’ in the oceans? What can we learn from that?
A future extraterrestrial civilisation may marvel at the grey cliffs of Dover after a layer of plastic nano particles has settled following the next inundation. They will be as happy to rediscover this research as I was to learn that chalk dust is harmless (potential Ig Nobel level work from ‘Guardian’).
https://www.theguardian.com/education/2011/nov/28/chalk-dust-health-research
Let’s also not forget water is the universal solvent.. given enough time it will dissolve anything.
From personal experience and over half a century of observation, I have noticed that the indigestible gets a passthrough for some other critter to chew on. Fast forward to the bottom of the food chain (no pun intended) in some deep ocean trench where the undigested residues of the indigestible are gathered, there they will be subducted into the planet’s own recycling mass-burn furnace.
From where after an aeon or two, even the most indigestible plastic residues will return volcanicly to the surface reduced to their original natural components…. just an hypothesis!
Cheers
Bahamamike
Pochas94
Crude oil from the Gulf disaster was not consumed by bacteria.
I have it on the best authority:
It all ended up in the “Bermuda Triangle”.
🙂
Bob Hoye
Microbes eat the little bits of plastic. This has been known since 2011 — why it is repeatedly ignored and unreported in Oceanic Plastics research is a mystery to me. The smaller the bits, the faster it is consumed by microbes.
In this study, they fed krill tiny bits of brand new plastic, un-degraded by time, sun, water and not yet partially digested by microbial action.
There was no evidence of digestion of plastic by krill. The krill just mechanically fragmented the plastic beads.
However, once excreted by krill and subsequently digested by microbes, the plastic isn’t plastic anymore — its just chemicals — like everything else.
But I LIKE paying $0.10 per paper bag at my local Safeway store. It makes me feeeeeeel good about myself. That I am saving the world’s oceans from all the third world trash … wait … you mean my plastic bags all were neatly deposited into the sanitary landfill that I pay $52.00/mo. to use? Nevermind. But I am STILL gonna feeeeeeel superior to you.