If you love seafood, then just know that they’re capable of being more than just your favourite zi char or mala dish. Some marine life – specifically shellfish and certain species of fish – actually have a real job: monitoring the purity of your drinking water!
In Warsaw (Poland), clams are used to monitor the city’s water quality, while in Minneapolis (USA), it’s mussels. Even Singapore is in on the game: we use… fish!
Clamming up for duty
The city of Warsaw gets its water from a river and the main water pump has 8 clams that have triggers attached to their shells. But not any clam will do. In fact, each clam that works for the Polish government is carefully selected by scientists from the river and undergoes an acclimatisation process.
Then, they’re placed in a specially designed flow tank and connected to a computer that monitors the degree that the clams’ shells are open. You see, these little molluscs close their shells whenever they detect a deterioration in the water quality in order to stop feeding and protect themselves.
If the water gets too toxic, they close, and that triggers the shut off of the city’s water supply automatically!
Even though the clams can live for about 30 years, the 8 clams on Warsaw’s payroll don’t work forever: they only serve for 3 months so that they don’t get used to the water that’s being tested. After their time is up, they’re sent back to the same water they were taken from – their shells are marked so that they don’t accidentally get picked up for reservist (or as someone’s seafood dinner).
There’s actually a whole documentary on Warsaw’s 8 little calms, called “Fat Kathy” (link here). The film follows the main scientist, a malacologist (a name for a mollusc expert, not someone who eats seafood mala for research), who watches over the system’s operation.
American mussels
Meanwhile in the American city of Minneapolis, the department of Water Treatment and Distribution Services have been employing the services of 12 mussels more than 10 years ago, and the city hasn’t had a major contamination that’s triggered the alert system.
The city’s water is from the Mississippi River, as are these mussels. These dozen molluscs are snuggled up in a tank, with the river water continuously being cycled through them. Since they’re filter feeders, they literally feed off of the water by pulling the nutrients down. And if these shellfish come across anything funky – like heavy metals – they close up shop like their clam cousins. As you’ve guessed it – it triggers the sensors attached to their shells to alert the scientists.
Like their clam cousins, the mussels – which can live for 50 years – will be set free in the river after they outgrow the tank and served their duty.
Singapore and its fishy methods
You can thank the fish for the safe drinking water that comes out of our taps. Singapore also monitors its water quality with marine life, although we use fish instead of shellfish.
The Lower Seletar Waterworks treatment facility uses colourfully-striped freshwater tiger barb fish, which are native to this part of the world and prefer clear, highly-oxygenated water. You may have also seen this species around your local aquariums, as it’s popular as a pet (but they’re not as expensive as these fish).
The facility monitors the fish with a camera (to check for abnormal behaviour) and tracks the number of fish in each tank. It’ll trigger an alert if half of the 20 fish in each tank die. Pretty dramatic way of “dying on the job” right?
Their job at Seletar is to ensure that the chemicals added to the untreated water is at a safe level, and works alongside a system monitoring the treatment process. These fish monitors have been deployed at locations like service reservoirs, waterworks, as well as the Causeway. And it must work, because these fish have been monitoring Singapore’s water supplies since 2012!
It’s thanks to this robust monitoring system that Singapore was ranked first among 180 countries for providing safe and clean drinking water, according to an index by US-based Yale University in 2024. Singapore scored 99.9 points, followed by Italy and the United Kingdom which both scored 98.2.
Biomonitoring
This method of monitoring water quality is called biomonitoring, and it uses living organisms, like plants or shellfish, to assess water quality. These critters can detect pollution levels the way our noses and tastebuds can’t. In fact, clams actually respond rapidly to changes in the water quality much faster than standard scientific tests for toxins.
Most countries employ physical and chemical sensors in the real-time monitoring of water supply. However, these sensors are expensive to maintain and reveal only local, short-term water quality changes. Moreover, the water may also contain unpredicted pollutants and a wide diversity of unknown chemicals, so they often go undetected.
All of these reasons is why employing the help of marine life makes sense – they’re among the fastest and most sensitive indicators of pollutants, and their monitoring is usually non-invasive and relatively inexpensive.
Shellfish aren’t just used in the monitoring drinking water quality – they’re also being used worldwide to both monitor and improve the quality of water. For example, mussels are monitoring the waterways in Western Australia’s Upper South West regions to reduce the frequency of fish kills. Cape Cod in northeastern USA is employing the help of oysters to clean up its beaches from nitrogen pollution that comes from island’s septic tanks.
Who says seafood is boring? The next time you’re tucking into your seafood meal, remember that these little fellas could have important jobs – and they work for free.
