The Clams of Poland’s Municipal Water Plants (and Other Biosensors)

Lambert here: Patient readers (and moderators) I’m leaving the comments on for this one, because my biosphere posts often get comments from teachers, and people who are far more knowledgeable than I am. Please stay on point. –lambert

By Lambert Strether of Corrente.

In my perambulations through the biosphere, I haven’t written about animals before, so I guess writing about whole-critter biosensors is a good way to open the New Year. This article, from Bored Panda seven months ago, surfaced again on my Twitter feed: “Someone Explains How Poland Uses Clams To Control Its Water Supply And It’s Pretty Crazy“:

[C]lams are placed in a specially designed flow tank. They are connected to the system controller that sends data to a computer which records the degree that the clams’ shells are open all the time. If the water quality deteriorates, the clams close their shells to isolate themselves from the contaminated environment. That automatically triggers an alarm and shuts down water supply while scientists perform laboratory tests…. This Polish Waterworks company claims that this biomonitoring method is one of the most effective proven technologies for water quality testing. According to them, mussels monitor water quality for over 8 million people in Poland.

(Poznan, Łódź, Warsaw, and Silesia use the same system.) System set-up aside, this concept works because clams[1] are “filter feeders.” From the University of Florida “Florida Shellfish Aquaculture Online Resource Guide“:

As clams feed, they create currents that move water in and out of the animal. Tiny moving cilia (hair-like structures), which cover the gills, pump water through the clam, drawing it in the incurrent siphon. Suspended particles in the water are captured by the gills and moved to the mouth for ingestion. The cleared water is then ejected from the excurrent siphon. By this very act of feeding, clams filter phytoplankton (microscopic algae or plants), microorganisms, and detritus. In doing so, they improve water clarity by reducing sediment loads and turbidity and removing excess nutrients from inshore coastal waters. Clearer water allows more sunlight to penetrate, which aids in the growth of important seagrasses and increases oxygen. “Filter feeding” clams may also potentially prevent harmful algal blooms.

So it stands to reason that clams don’t like to filter polluted water, and will close if they sense it. In a current article, Polish News describes the flow tank set-up more precisely: “Poznan. The clams filter the water. They check whether the water is polluted or clean.” From Dorota Wiśniewska, spokesman for Aquanet SA in Poznań:

The mussels are glued[2] to the plastic pedestal. In addition, a magnet disc is glued to the shell, and a probe is mounted nearby that detects changes in the magnetic field. When the clam closes or opens, it touches the probe with this magnet, [arming the alarm system]. If two or three clams close, it doesn’t have to mean anything, but if there are eight, [the alarm fires]. Then our role is to find out what has upset them so much and find out if it is a real or a false alarm

Here is an image of the set-up (credit: Fat Kathy, who did a documentary on the Warsaw clams), showing the pedestal, magnet, and probe:

The advantage of this natural, “whole-animal” system is that it’s holistic; it detects pollution as such, not specific types of pollution. Still from Poznan, Grzegorz Podolski, senior technologist for water quality at Aquanet:

When looking at chemical tests, you can check a lot of things, but for each type of test you need a separate device – says Grzegorz Podolski, senior technologist for water quality at Aquanet. It is different with biomonitoring. – Here one organism, in this case a clam, checks many parameters and if there is any chemical contamination, it lets you know. And that’s enough to take a sample, take it to the laboratory and see what it is about: confirm or deny that something is happening to the water. It is a system that ensures safety against pollution and even terrorist activities.

Here in the United, Minneapolis uses the same system, our only city to do so. From Minnesota Public Radio:

Plant staff monitor the mussel activity on a computer graph. If they were to suddenly close, workers would test the water to find out what’s happening — the mussels don’t indicate the precise source of the contamination, so human sleuthing comes next — and could even shut down the plant while they investigate the problem.

The mussels in the Minneapolis water treatment plant are decidedly simple when compared to the plant’s complex system of chemical reactions, filters and lab tests that treat the region’s drinking water. But [George Kraynick, the city of Minneapolis’ water quality manager and laboratory supervisor] said they are a great way to measure what’s going on in the river.

“It’s 24/7. It’s using nature,” he said. “It’s very low tech and it’s really almost bulletproof, because these guys are going to know when something’s in the river.”

“We like to say they’re the canary in the coal mine,” said Teresa Newton, a biologist and expert on native mussels who works with the U.S. Geological Survey. “When you find healthy and diverse populations of mussels in streams, it’s a good sign that the sediment and water quality is pretty good.”

(We’ll get to canaries in coal mines later.) So, as readers know, I like simple and rugged. (That’s why I like universal concrete material benefits). This system is as simple and rugged as a household thermostat (and not one of those Internet of Things abominations). But did the system have a name?Then I read this tweet, curated by Bored Panda:

(Sotala is, for good or ill, an artificial intelligence researcher.) So, what we have here is a biosensor! But just to double-check, I started looking for the definition of biosensor. From the Shorter Oxford English Dictionary:

A thing for detecting chemicals by the use of a living organism or a product of one; an organism used for this purpose.

So, “thing for detecting” is the system; the “living organism” is the clam. Wikipedia agrees, kinda:

A biosensor is an analytical device, used for the detection of a chemical substance, that combines a biological component with a physicochemical detector.

Here we move away from “living organism” to “biological component”, although the clam is a “biological component” of the whole system. Here, however, we move away from “biological component” to “biological receptor/biorecognition element, such as nucleic acids, antibodies, enzymes, cells and even microorganisms” (certainly not clams):

Biosensors are small devices that utilize biochemical reactions mediated by a biological receptor/biorecognition element, such as nucleic acids, antibodies, enzymes, cells and even microorganisms, and usually detect targets based on optical, electrical, thermal and other signals (Chen et al., 2019). Biosensors are characterized by a fast response, low cost and potential miniaturization with other portable devices that can be operated by nontechnical personnel to measure target parameters using a small number of samples on site (Ejeian et al., 2018).

And finally we abstract away the organic altogether:

A biosensor is a machine that measures biological or chemical reactions of the analyte by generating proportional signals to its concentration. Biosensors are used in many applications such as disease monitoring, new drug research, and biomarker indicating the presence of the disease in the body fluids like blood, urine, saliva

As if living organisms couldn’t be part of the loop and detect “biomarkers” in blood, urine, or saliva!

So, in looking at definition of biosensors, we have a spectrum that ranges from systems that include living organisms to machines. (There’s an entire line of business in “wearables” that call themselves biosensors). I can only speculate on why this should be, but I would bet it’s a lot easier to make a profit on mahines, nucleic acids, antibodies, enzymes, and miniaturization than on clams. Clams are hardly innovative.

That said, I want to stick with biosensors that are whole animals because they’re simple and rugged (and hence suitable for post-Collapse scenarios). The very obvious first example, mentioned above, is the canary in the coalmine. From Forbes, “The Canary In The Coal Mine Isn’t Ancient History“:

Coal miners face many constant dangers: cave-ins, explosions, fires, and dangerous gases like carbon monoxide. The gas is odorless, colorless, and tends to replace oxygen molecules in the bloodstream, which keeps actual oxygen molecules from reaching organs and tissues. At first, carbon monoxide poisoning just causes a mild headache, dizziness, and shortness of breath, but it can quickly become fatal. And because burning coal and wood is a perfect way to release carbon monoxide into the air, coal miners are especially at risk.

But canaries, it turns out, are much more sensitive to carbon monoxide and other poisonous gases than humans. Around 1911, miners started carrying canaries into the mines with them, and they quickly became a metaphor for warning signs – when the canary keels over, it’s time to evacuate the mine before you become the next victim.

By 1986, though, only about 200 canaries were still being carried into British coal mines. The new digital detectors were cheaper and more effective, but they seemed to lack something when it came to comfort and companionship.

“They are so ingrained in the culture miners report whistling to the birds and coaxing them as they worked, treating them as pets,” reported the BBC in 1986, describing miners “saddened” by the decision.

I had no idea that canaries were introduced into coalmines as late as 1911! (How that came to be would be a fun topic I have no time for now). But as the clams warn of pollution after filtering water, so the canaries warn of polluion after breathing air.

My second example of a whole animal biosensor is, of course, the covid-detecting medical dog. We have a number of projects under way. From the Guardian, “‘Covid-19 has an odour, and the dogs are detecting it’: meet the canine super-squad sniffing out the virus“:

James Logan [of the London School of Hygiene & Tropical Medicine ]has been working in disease control for 20 years, and has a particular interest in the odour associated with disease. “We’ve known about this for hundreds of years. There are historic reports of medical professionals diagnosing people just by sniffing them,” he tells me. “Reports that yellow fever smells like a butcher’s shop, TB smells like stale brown bread.” More recently – and more scientifically – studies have demonstrated that respiratory viruses can be distinguished by the odour they cause the body to produce. “Viruses themselves do not produce odours. When the virus has infected our cells, this can have a knock-on effect on various systems within the body, which results in odours being released through our skin and breath. So there was a really strong likelihood that coronavirus would produce a distinct odour as well.”

[Claire Guest, a behavioural psychologist working with Logan at Medical Detection Dogs] points out that, back in 2004 she worked on the first scientific study that showed dogs can detect human bladder cancer, which was in fact published in the BMJ. Recently, she’s worked alongside Professors James Logan at the London School of Hygiene & Tropical Medicine, and Steve Lindsay of the department of biosciences at Durham University, among others, on a successful project to train dogs to identify malaria.

We are not looking to replace clinical testing,” Logan says. “We are keen to use dogs in very specific circumstances, where we need to get through a lot of people quickly. Airports, sports stadiums, train stations, universities, care homes.” Guest points out how useful it would have been to deploy Covid dogs at the airports early on in the pandemic, with all those flights coming here, bringing in so-called “super-spreaders”.

They’re not quite at the stage of releasing their results yet, but aim to publish as soon as there is enough data to robustly show how well dogs can detect coronavirus. There will be several independent reviews before anything is put into practice. But everyone – Guest, Lindsay, Logan, the trainers – is positive about the way the first phase, the proof-of-concept study, is going. “There is no doubt now that Covid has an odour, and the dogs are detecting it,” says Logan. The dogs will soon start to train with people, and in different situations – outside, in queues, crowds, including at an airport, hopefully Heathrow – says Logan. “It will be about getting the dogs working in an environment where there will be tannoy announcements and other distractions.” They hope this will happen early next year.

There are parallel efforts in Italy and France, but only the UK study has received funding. A parallel effort in the UK reports in the British Medical Journal, “Scent dog identification of samples from COVID-19 patients – a pilot study“:

As the COVID-19 pandemic continues to spread, early, ideally real-time, identification of SARS-CoV-2 infected individuals is pivotal in interrupting infection chains. Volatile organic compounds produced during respiratory infections can cause specific scent imprints, which can be detected by trained dogs with a high rate of precision. Eight detection dogs were trained for 1 week to detect saliva or tracheobronchial secretions of SARS-CoV-2 infected patients in a randomised, double-blinded and controlled study. The dogs were able to discriminate between samples of infected (positive) and non-infected (negative) individuals with average diagnostic sensitivity of 82.63% (95% confidence interval [CI]: 82.02–83.24%) and specificity of 96.35% (95% CI: 96.31–96.39%). During the presentation of 1012 randomised samples, the dogs achieved an overall average detection rate of 94% (±3.4%) with 157 correct indications of positive, 792 correct rejections of negative, 33 incorrect indications of negative or incorrect rejections of 30 positive sample presentations.

Close enough for government work? And in real-time? Business Insider estimates 750 tests per hour per dog. So, 10000 / (750 * 5) = 2 means that 5 dogs could sort a crowd of 10,000 in two hours. That’s fast enough for, say, a campaign rally or a concert. Of course, you’d need a lot of trained dogs nationally, but why is that a bad thing?

There are other possibilities, as of birds for electromagnetic fields, but for now, our whole-animal biosensors are clams, canaries, and dogs. Do readers have more suggestions or examples? (I believe a biosensor has to act in real time, like a furnace’s thermostat or a canary keeling over; so not every animal — or plant! — that reacts to pollution, say, or drought is a biosensor.)


[1] Warsaw is said to use clams, Poznan mussels. I don’t know whether this is a translation issue, or whether each city uses a different species of filter feeding bivalve. This “cooking community” says that clams live in fresh water, and mussels in fresh or salt water.

[2] After their two months tour of duty, the clams are returned to their original beds, marked so they aren’t recruited again.

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About Lambert Strether

Readers, I have had a correspondent characterize my views as realistic cynical. Let me briefly explain them. I believe in universal programs that provide concrete material benefits, especially to the working class. Medicare for All is the prime example, but tuition-free college and a Post Office Bank also fall under this heading. So do a Jobs Guarantee and a Debt Jubilee. Clearly, neither liberal Democrats nor conservative Republicans can deliver on such programs, because the two are different flavors of neoliberalism (“Because markets”). I don’t much care about the “ism” that delivers the benefits, although whichever one does have to put common humanity first, as opposed to markets. Could be a second FDR saving capitalism, democratic socialism leashing and collaring it, or communism razing it. I don’t much care, as long as the benefits are delivered. To me, the key issue — and this is why Medicare for All is always first with me — is the tens of thousands of excess “deaths from despair,” as described by the Case-Deaton study, and other recent studies. That enormous body count makes Medicare for All, at the very least, a moral and strategic imperative. And that level of suffering and organic damage makes the concerns of identity politics — even the worthy fight to help the refugees Bush, Obama, and Clinton’s wars created — bright shiny objects by comparison. Hence my frustration with the news flow — currently in my view the swirling intersection of two, separate Shock Doctrine campaigns, one by the Administration, and the other by out-of-power liberals and their allies in the State and in the press — a news flow that constantly forces me to focus on matters that I regard as of secondary importance to the excess deaths. What kind of political economy is it that halts or even reverses the increases in life expectancy that civilized societies have achieved? I am also very hopeful that the continuing destruction of both party establishments will open the space for voices supporting programs similar to those I have listed; let’s call such voices “the left.” Volatility creates opportunity, especially if the Democrat establishment, which puts markets first and opposes all such programs, isn’t allowed to get back into the saddle. Eyes on the prize! I love the tactical level, and secretly love even the horse race, since I’ve been blogging about it daily for fourteen years, but everything I write has this perspective at the back of it.


  1. Dan

    Lovely article. On your last point, it is totally false that all clams live in fresh water. For instance, here in California there are many genera of ocean shore clams (Saxidomus, Siliqua, Tressus, Macoma) and I’d be hard pressed to name a fresh water one (an example of my ocean bias more than biology knowledge!)

  2. John Emerson

    What I think we should say is that clams and other filter feeders are discriminating about pollution. What the filter out plankton, algae, etc., which is the pollution they live on, and purify the water that way, but reject other sorts of pollution.

    The zebra mussels have clarified the water in the Great Lakes, but have done nothing to reduce chemical pollution, etc., and also have had many other harmful effects.

    It would seem that in general filter feeders are the most environmentally responsible of animal foods as long as you don’t over harvest.

  3. Handles

    This woman from Scotland can detect Parkinson’s disease by smell, years before a clinical diagnosis can be made:

    I love this anecdote from the original report ( of blinded testing of her ability: “Initially Milne’s result showed 11/12 detection success, however, the control subject she misidentified was later diagnosed with PD, increasing her accuracy to 100%.”

    While Joy herself could be counted as a “whole animal biosensor”, its more relevant to the above article to speculate about where future research could end up. Current research includes Medical Detection Dogs ( or “electronic noses” (

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