Guest Essay by Kip Hansen – 25 October 2020
What is pictured in this little image? And what can it possibly mean?
These are very good questions and should be asked whenever the lede of a science news story is based on an image.
Why? “A picture is worth a thousand words” – – – or so they say. If that is true, then pictures can also fool us a thousand times more easily than mere words.
Now, a picture of a new species, say a confirmed photograph of Bigfoot or the Loch Ness monster, might be appropriate for the news. But I am always skeptical when a science news article is based on an interesting picture, purporting to tell us something important.
The example I am using for today’s essay is related to my recent essay titled: Where Do the Plastic Bottles Go?. In that essay, I reported that pelagic plastic (plastic floating in the oceans), exposed to the sun and the waves, breaks down into smaller and smaller pieces which in turn are literally eaten by microbes – such as bacteria. In other essays on plastic in the oceans, I have asserted that “the natural system finds a way to use most everything – in the case of oceanic plastics, as homes and food.”
After Where Do the Plastic Bottles Go? was published, our very own CTM sent me a link to this paper:
“Microbial carrying capacity and carbon biomass of plastic marine debris” by Shiye Zhao, Erik R. Zettler, Linda A. Amaral-Zettler and Tracy J. Mincer. The full text version is, unfortunately, pay-walled, but a EurekaAlert! story gives us the image used above and a good summary.
“Trillions of plastic debris fragments are afloat at sea, creating the “perfect storm” for microbial colonization. Introduced more than 50 years ago, plastic substrates are a novel microbial habitat in the world’s oceans. This “plastisphere” consists of a complex community comprised of bacterial, archaeal, and eukaryotic microorganisms and microscopic animals.”
What does that mean when we get up in the morning? It means that sea creatures of all types – tiny, mostly microscopic, little plants and animals – start living on the surface of these bits of plastic that are floating around in the ocean. The bits become floating homes for these creatures and plants – they live on the surfaces of the bits in what are called “biofilms”.
The new and original part of this study is that “Using confocal laser scanning microscopy with sophisticated imaging software, researchers directly obtained data ranging from cell counts, size and the characterization of microbial morphotypes to complete three-dimensional constructs.” It is the laser scanning microscope that produced the following image:
As I note below the image, I have adjusted the contrast and color levels to enhance this image – the original is rather dark. It is from photos like these that the researchers have counted the little critters living on the surface of this bit of plastic and formed an idea of how many of what kinds of them are present.
Why have they done this? They think that biofilms forming on the itty bits of plastic found in the world’s oceans are a threat:
“As an unnatural addition to sea surface waters, the large quantity of cells and biomass carried by plastic debris has the potential to impact biodiversity, autochthonous ecological functions, and biogeochemical cycles within the ocean.”
In other words, the plastic bits, found in the top layers of the oceans, supply a happy home for lots of microscopic “bacterial, archaeal, and eukaryotic microorganisms and microscopic animals” – a home that didn’t exist (as far as the researchers know) before the availability of all those little pieces of plastic. Their worry is that all that “extra” life will use up the resources of the other life that previously inhabited the upper layer of the ocean causing – gasp – change.
I am not very interested in their worries about too much life or their dread of the possibility of change. My interest is that these researchers claim to have “quantified” not only the number of microscopic cells living on all of the little bits of plastic floating in all of the world’s oceans, but to have “quantified” the “the total amount of carbon biomass in these plastic-associated cells”.
How did they do that?
From their paper:
“In situ incubations consisted of placing postconsumer plastic from 1-gallon milk jugs (PE), disposable cold-drink cups (PP), disposable hot-drink cups (PS), and glass cubes off a dock in Woods Hole, Massachusetts, in Vineyard Sound (GPS coordinates: 41.525, –70.673). The items were cleaned and then sterilized using 70% ethanol prior to placing them in the seawater, ~1 m below the surface in July 2013 in 1-cm mesh nylon cages to prevent plastic samples from escaping. Subsamples (~5 × 5 mm) were taken at periodic time points (1, 2, 3, 8, 12 weeks of immersion).”
They what? They put pieces of different plastic (and in one case, a glass cube) in little plastic mesh cages and hung them off a dock at Woods Hole, Massachusetts. They left them there for 3 months, periodically taking little samples from each. They used the fancy confocal laser scanning microscopy to count the cells and types of cells on each piece. And then:
”Although several studies have surveyed microbial diversity and quantified specific members of these biofilm habitats, ours is the first to holistically quantify total cell inventories under in situ conditions. . . . . Based on the reported plastic counts and size classes floating in the world’s ocean and the general abundances of different plastic debris in ocean surface water, we estimate that PMD [Plastic Marine Debris] could provide a total surface area of 2.5 × 1010 m2 (Table S4).
Integrating over the calculated PMD distribution in the world’s ocean, we estimated the total number of cells on plastic debris to be 2.1 × 1021 to 3.4 × 1021.
Multiplying plastic surface area by the area-specific carbon biomass at the early and late stages of biofilm on plastic substrates, the total amount of carbon biomass in these plastic-associated cells is predicted to be 1.5 × 103 to 1.1 × 104 metric tons, which is roughly similar with the previous estimate of living biomass (8.6 × 102 to 1.6 × 104 metric tons) on PMD. Our higher bound carbon estimate (1.1 × 104 metric tons) approaches the estimated cellular carbon mass in the global rivers (2.4 × 104 metric tons), as well as both polar regions (8 × 104 metric tons).”
That’s right, using their single-location, one-time samples, they have calculated, quantified, the total living biomass to be found on all of the plastic bits in all of the world’s oceans.
Marvelous, isn’t it? Who would have thought it would be that easy to guess the total weight of all those little microscopic plants and animals on the trillions and trillions of (uncounted) little bits (of unknown sizes) of plastic swirling around in the oceans.
I have no idea of the accuracy of this research group’s counts of microorganisms living on the bits of plastic they hung off the dock at Woods Hole.
But as for the rest, the magical mystical calculations based on things uncounted and unsampled?
I call that:
Computational Hubris:
“An inordinate and unjustified trust, or faith if you like, in the power of advanced computational machines and processes to produce highly accurate and extremely precise results from relatively inaccurate and imprecise, highly uncertain data using techniques and methods that have not been tested nor verified to be suited to, or sufficient for, the purpose.”
— Kip Hansen
They have not only manufactured the quantities but they have manufactured a threat from their manufactured quantities.
And that’s no way to do science.
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Author’s Comment:
All of you who have experience snorkeling in tropical areas, or using SCUBA*, even in colder waters, will know that to turn a “sand desert” into an underwater oasis only requires the placing of almost ANY solid object on the sea floor. Even a single rock the size of an orange becomes a mini-sea-life oasis, with plants, animals and fishes. Sink a WWII destroyer and you have a huge living reef in a few months.
This story tells us that even bits of plastic floating around in the top couple of meters of the seas, almost all smaller than 8 mm (3/10th inch) and most smaller than 4 mm (just over 1/10th inch), become homes for sea critters of all kinds. The story fails to tell us that many of those critters are actually using the plastic not only as a home, but as a food source. And, of course, many critters are eating the other living things on the plastic bits or using their biological excreta as food.
I trust that the purposes of Nature will be fulfilled. And providing novel homes for more life probably isn’t a bad thing.
As an aside, this research is done in the relatively cold waters of Woods Hole, Mass. They get a little thin biofilm over 3 months. The bottom of my boat, despite poisonous anti-fouling paint, would collect inches of living material every month in the Virgin Islands – all kinds of growths and sea creatures that lived on and in the growth. While cleaning the bottom one time, a little crab crawled into my ear, scuttling sideways.
Remember, just because Nature will clean up our messes, given enough time, we should keep all of our trash, including plastics, contained and disposed of properly. None of it should end up in the sea.
Address you comments to “Kip…” if speaking to me. Thanks.
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* = Self Contained Underwater Breathing Apparatus
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Kip, I am a sailor like you, have sailed the coast of North America from Desolation Sound to Zihautenejo, Mexico. There are plastic bags, styrofoam containers, and floating nets out there, but not in Canada or the US. Where is the junk? In Mexico or any third-world country. The people of Mexico are starting to take an interest in the environment but it hasn’t sunk in as yet. And even with the stuff you find floating near a city or town, the rest of the ocean a few miles away is empty. If we could just raise the standard of living of all the emerging countries I think the ocean junk would mostly disappear.
Michael Nagy ==> Very true, almost all oceanic plastic is coastal and comes from poor nations unable to afford to organize adequate trash pick up and handling. The vast majority in SE Asia and Africa, but a lot from the Phillipines, the Caribbean, and South and Central America as well.
the total amount of carbon biomass in these plastic-associated cells is predicted to be 1.5 × 10^3 to 1.1 × 10^4 metric tons,
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1.1 x 10^4 metric tons worst case??
Since all this carbon is floating it must be lighter than seawater. Assume it is close to the density of fresh water which is reasonable for living organisms.
A metric ton of fresh water is a 1 meter cube. We are talking about a cube 22 meters on an edge for rhe entire ocean. That would weight 1.1 x 10^4 metric tons.
A 22 meter cube! In the scale of the oceans this is invisible.
I wonder if they couldn’t have saved a lot of time, although not have gotten the same publication, by looking into the microcarriers used with bioreactors. These systems are often used for vaccine production and have been in commercial use for decades.
https://www.sciencedirect.com/science/article/pii/S2214031X15000182
Kip, please follow my reasoning while trying to evaluate the magnitude of the numbers they throw in the paper:
After reading the paper I became much more optimistic regarding the “threat” of microplastics in oceans. The numbers given are the very demonstration that there is no danger whatsoever. Just for comparison:
They say: total mass of plastic in oceans: close to 270 thousand tons.
Apple production in the world: 86 MILLION tons
Apple production in the USA: close to 5 MILLION tons
Apple production in my country (Portugal): somewhat over 300 thousand tons.
So, the amount of microplastics in oceans would be less than the apple production of my little country; or about one half of the Portuguese production of pears and apples. I try to imagine all those pears and apples from Portugal distributed in the world oceans: how many fruits per square kilometer?
Replacing apples with plastic balls the same size and mass, 270 thousand tons of medium sized balls correspond to ca. 1700 million pieces. The total area of oceans is ca. 362 million sq km. So, if we threw 270 thousand tons of plastic balls to the ocean and distribute them evenly, we would have a chance of finding four or five in each sq km: much cleaner than in most cities…
Also, in the paper they use biomass (instead of mass or fresh weight) of organisms, and say that the carbon biomass covering the plastic debris in oceans may be a bit over 11 thousand tons. That is equivalent of the carbon (element C) content of roughly one million tons of apples or pears, thus about 1/5 of the apple production in the USA and 1/86 of the apple production in the world. Or equivalent to about 1/370 of the world potato production; or to 1/3000 of the total world rice production.
Repeating the thought experiment, now with real fruit, and if we threw one million tons of fruit in the ocean, that is roughly 7 million fruits; if they were evenly distributed, we would have a chance of finding about one fruit per 5 sq km: a lot of “pollution”, as they say, enough to (mind their words, please!) “have the potential to impact” everything plus the kitchen sink.
So, either the numbers in the paper are grossly underestimated, or the size of this “threat” to the environment is risibly minuscule…
Joao Martins ==> Excellent analysis, of the very best sort. Using real things that others can visualize and with which they are familiar.
I spent a number of years in Portuguese ports and was in Lisbon for the revolution. Exciting times, many stories — some best not told. Lisbon is my very favorite city, and Funchal, Madeira one of my favorite ports — spent many a Christmas here.
I still can’t work out whether Kip is complain that the number is too big or too small. The first
half of the essay appears to be claiming that the number is too large, while the second half is
all about how quickly organisms colonise rubbish in the ocean.
There appears to be nothing wrong with this paper. They perform an experiment, make a measurement
and then use it to make a prediction. The result of their prediction regarding the total mass is then
compared to other estimates and they find that the estimates agree. Surely if you want to complain about
this then you would also have to disagree with almost every single bit of cosmology. Take the evidence
that universe is expanding for instance. Hubble measured about 50 galaxies fitted a straight line and
then claimed that the universe was expanding. Similarly the claim that the Andromeda nebula was a seperate
galaxy was based on an observation of a single star.
Izaak Walton ==> I complain about neither too large or too small.
My point is that from one single sample at Woods Hole during one time period of 3 months that they claim to have calculated a quantity for total carbon biomass of all the biomass to be found on all of the unknown number of pieces of unknown sizes of all the unknown amount of pelagic plastic in all of the world’s un-sampled oceans. They have not even measured the actual biomass on any single piece of free floating plastic from any ocean anywhere.
They then use estimates of the number of pieces of various types of plastics in various oceans from studies that perform the same nonsensical computational gymnastics to arrive at some that number.
If these numbers were based on any sort of real world sampling of real bits of plastics actually found in real oceans – sampling that produce estimates that could be checked against reality — say by coming up with an estimate of what should be found in a 5 km transect of the Pacific at a certain latitude — and then doing that transect and checking the numbers….well, then they would be getting somewhere.
Their method sounds good, doesn’t it. X amount of biomass per mm2 times calculated mm2 of pelagic plastic == Total Biomass!
Except that NONE of these numbers are real in any normal scientific sense. Multiplying very vague and unsupportable numbers does not result in a real world answer.
Kip,
Making a measurement over a 5km transect of the pacific would be time consuming and
almost certainly a huge waste of money. This estimate is simple, cheap and almost
certainly good enough to most purposes. As such it is a good use of simple measurements and statistics to reveal something about the world.
Almost all science is based on a combination of sampling and use of statistics. Astronomers claim
that roughly 75% of mass in the universe is Hydrogen. And they do that on the basis of measuring a tiny number of stars. Biologists estimate the number of insects using a small number of traps etc. Doing anything else is generally just not possible. Even something as simple as the number of atoms in a mole of gas is based on the same idea, make a small measurement and then extrapolate to something bigger.
Izaak: Number of molecules in a particular gas is very precisely known. Briefly, oxygen gas with a molecular wt of 32 has a molar wt of 32grams. In turn, 32grams of oxygen will have Avogadro’s Number (NA = 6.02214076×10^23) of molecules. Carbon dioxide, with a molecular wt of 44, has, accordingly, a molar wt of 44grams, and this latter will also contain Avogadro’s Number of molecules.
Gary,
Avogardro number is not particularly precise — there is an error of more than 10^15
atoms or molecules. The point is that it is an estimate done using precisely the method
that Kip is complaining about — you measure a small number and multiple by another estimate to get something else. In this case we can estimate the error and it is unimportant for almost all applications.
Izaak: The atomic, ionic and molecular sizes are well measured (ions less so and some are compressible). If they are not well measured, tell me how your small samples will be counted? I havent checked your claim on 10^15 error, but do you know how small 10^15 is compared to 10^23? Let’s see in percentage terms: (10^15/19^23 ) x 100= 1/1,000,000 %.
Let’s simplify the description.
Organic life readily forms colonies on organic matter…
That is not a surprise, at all.
That organic life consumes organic matter is also not a surprise.
Nor is it a surprise that students looking for eureka discoveries of the most mundane topics, suddenly read world doom and gloom in their mundane research.
ATheoK ==> Yeah, but the REAL problem I see in this is not that they find more gloom and doom, but that they think they actually quantified something real. It is the whole approach and method that is wildly wonky (those are scientific words for just plain nutty).
I can’t think of an analogy crazy enough to describe what they have done (and the researchers before them that claim to have calculated the number of bits and the surface area of those bits).
How about:
1. Stop ten men on the streets of Boston.
2. Count the number and value of coins in their right hand front trousers pocket.
3. Using census data from every nation in the world, find the “number of men in the world”
4. Use relative economic status of various nations to adjust for differing monetary values.
5. Multiply all the National Trouser Pocket Change values by Number of Men for each Nation, then add them all together.
6. Voila! we have quantified the Total Pocket Change of the World’s Men.
Kip,
There is a difference between quantify and predict or estimate. In the quotes you provide the
authors are state clearly “we estimate …”. There is nothing wrong we making an estimate in
this way. Looking at your example for the total pocket change, a statistican could tell you
the likely error in your estimate and also how many more people you would need to sample
in order to reduce the error below any desired bounds. You can then decide whether it is worth
the time or effort to do so.
Izaak Walton, Kip:
What is wrong is, what the authors of the paper do is not realy an “estimate”. An estimate is valid only inside the domain interval of the independent variables where the observations were made. What they have made is something very dangerous: an “extrapolation”. I.e., they have calculated, as Kip has been pointing out, something that is way out of the scope of the variables that was used to make the empirical observation (roughly: the “sample” used is NOT even close to being representative of the population to what they are extrapolating). In other words: when extrapolating, one MUST be extremely careful with the “ceteris paribus” principle: one MUST be sure that the characteristics and conditions of the universe to where he is extrapolating are very similar, not significantly different, from the conditions where the empirical observations were made. This is what Kip has been trying to call our attention to: the world conditions are very, very different from those wher they have put that small aparatus at Woods Hole: anyone can understand that.
What they did in this study is something like going to their child’s kindergarten class for a couple of weeks, observing their child and a couple of friends doing a few academic exercises, and then making estimates about all of the schools around the entire planet. Actually, it’s not even that good, because overall children are more alike than different forms/kinds of plastic are, and schools are more alike than the ocean climate across the globe.
If they were simply estimating potential growth on particular plastics in Massachusetts waters during a certain time of the year, their experiment might in fact be admirable. It would actually add knowledge, the experimenters would learn something, and science would advance. They could follow up with other kinds of plastics, different forms and shapes, other times of year, other locations (which would yield other kinds of microorganisms), and other mixing. But their crazy extrapolation in multiple dimensions is like the hubris of first-year student who took a stats class and knows how to run R or Python.
Science dies a little bit with each of these exercises in either Model Worship or Simplistic Extrapolation Explosion.
Kip, you said: “They have not only manufactured the quantities but they have manufactured a threat from their manufactured quantities.
And that’s no way to do science.”
I was immediately struck by the unhappy thought that that is largely how they do do science in our new post-normalcy. It ties in with your computational hubris observations. And it isn’t just the climate wroughters at work. The science re Covid may never be cleaned up. And black holes, string ‘theory’, dark matter and dark energy in cosmology, froddy cancer and other medical research….
BTW, I enjoy all your articles – what a fine teacher you would make. You may be amused to hear that I discussed your wonderful ladybug piece with my wife and the following day with air temperature around 12 -15C she came into the house followed by a 7 spot ladybug and we found a second one crawling on a sill above a cast-iron hotwater radiator. I have no idea where they are now and there are perhaps others. There is a lot of comings and goings through our front door.
Gary ==> Thank you for the ladybug story . . . I have sent in a photo of the 13 spot ladybug we found on the roses my wife cares for at a local mini-park.
Not everyone agrees with me. For instance, see above for Isaak Walton’s ideas on this (probably not his real name — Isaak Walton wrote “The Compleat Angler, or the Contemplative Man’s Recreation” in 1676….). He seems to think it is ok to use nonsensical non-data to make “estimates” as long as you call them “estimates”. To each his own.
I do admit that it is a very common practice throughout the sciences in the last couple of decades as computing power ramped up and became available. Seduced many a researching into believing that his computational results were something real.
I’m not even sure about calling it “computational hubris”. That’s too generous. I’d settle for scientific bollocks.
Some years ago (circa 2008) I saw fascinating presentation from a Woods Hole researcher showing how the “oceanic genome” of micro-critters at one East-coastal location varied enormously over not only seasons and months, but over weeks, days and hours.
Most assertions and conclusions are still just shooting in the dark.
“They have not only manufactured the quantities ”
no they have estimated the quantities. you have manufactured misunderstanding
your job is to try to replicate their findings by doing a similar field test in a different location.
you would ask questions like this?
does the type of plastic matter?
does the location matter?
Or you could do a different approach. you could go into the ocean and sample plastic, although
that would not tell you how long it takes the critters to coat a fresh piece of plastic
all science starts somewhere, and never ends
Mosher ==> My job, as a science journalist (essayist, more correctly) is to discuss and explain what I see in the science work of others — to praise what I see as good work, to criticize what I see as poor work, and to point out when offered science results are not scientific in fact.
It is the job of others in their field to attempt to replicate their work — which would be valid if they had done actual science.
Their science was good and valid as long as they were working with their samples and their fancy microscope and counting cells and cell types. That was good and valuable work.
They then went for “an extrapolation too far” — by claiming that through the magic of massive computation, they could quantify the biomass of all the biofilms on all the pelagic plastic in the world.
Good article Kip. It does sort of hint at what I imagined. Read about floating bed media filters in the aquarium hobby. All that surface area!
I have one in every tank.
“The items were cleaned and then sterilized using 70% ethanol prior to placing them in the seawater”
Their calculations are questionable based on this. 70% alcohol will kill virus particles but bacterial cells react to high levels of toxins by forming spores that “hatch” out when environmental conditions return to normal. If you want to sterilize objects for bacteria using alcohol you use a 5% alcohol solution. In this way the cells absorb a toxic level of alcohol and die before they detect the danger and have a chance to form spores.
I worked in manufacturing and we never used a higher concentration than 5% alcohol to sterilize equipment for this very reason.
AussieDon ==> An interesting technical point. Can you supply a reference? I’m interested in that idea (not really in reference to this study or essay.)
“we should keep all of our trash, including plastics, contained and disposed of properly. None of it should end up in the sea.”
And why exactly isn’t putting it in the ocean the proper way to dispose of plastics? It may be better than dumping it in a landfill.