Fluctuations in the heartbeat rates of crayfish are used to monitor the water for contaminants. When heartbeats increase, the water is stopped and checked. Source: Vadim Zhernov / RIA Novosti
Russian researchers have taken the Aussie red claw crayfish and given it an important role: protector of St. Petersburg – the second largest city in Russia, with a population of more than 5 million people.
Not all cities are fortunate enough to draw their potable water from well protected dams and reservoirs. Many European cities rely heavily on multi-step water-purification processes, and this is typically the case in Russia.
Even with sophisticated treatment systems, not all pathogens in the water can be eliminated or detected in time to ensure public safety. Detecting dangerous substances quickly, to prevent them from entering the water supply in the first place, can be critical in protecting the health of millions of people.
Physicochemical analysis of water quality only looks at a limited set of parameters and is relatively slow, not always producing results in real time. Biological indicators can play an important role as early warning systems – similar to the old concept of taking canaries into coal mines.
Vodokanal St. Petersburg supplies potable water to 5 million people. It uses crayfish in a bio-monitoring system that checks the River Neva's water quality. Source: PhotoXpress
Vodokanal, St. Petersburg’s water-supply agency, has chosen the river crayfish as its "canary” – one that can protect the population from unforeseen water contaminants or even, potentially, terrorist acts.
The crayfish are exposed to water at the source, before it reaches the point of purification, and if they display stress (indicated by an increase in heartbeat) the water supply from the source is interrupted and a water sample is automatically taken for chemical and biological investigations.
To measure the yabbies’ heartbeats, optical fibre connected to recording equipment is attached to their hard outer shell (or carapace). From there, the heart signal is recorded and digitised, much like a hospital ECG.
Vodokanal uses Russian native crayfish during cold weather, but they start to show signs of stress when the water temperature goes above 21C. In summer, when the water temperature rises, heat-loving Aussie yabbies are enlisted to do the job.
To understand how the crayfish (and their heartbeat) behave in normal healthy conditions, the animals were first monitored in clean, pollution-free water.
The monitoring led to two conclusions: the first, that only male yabbies of the 3-to-5-year-old age bracket were suitable for the job; the second, that female yabbies were more likely to have heartbeat fluctuations, especially during breeding time.
What’s more, the crayfish need to be resilient enough to not be stressed by living close to noisy water pumps and to be calm with people constantly observing, feeding and handling them – not to mention having an optical fibre permanently sticking out of their shell.
In summer, when the water temperature rises, heat-loving Aussie yabbies are enlisted to do the job. Source: Lori / Legion Media
To make the yabbies feel more comfortable in these unnatural conditions, Vodokanal set up its own yabby farm where their 10-legged co-workers are bred in conditions similar to their future workplace – that is, in a noisy environment, surrounded by human activity. This way, when the yabbies are placed in their work tanks, they stay calm and can maintain a steady heartbeat.
This innovative technology, developed at the Research Centre of Ecological Safety, at the Russian Academy of Science, has been successfully operating in St. Petersburg and its satellite cities for almost eight years.
This kind of bio-monitoring is not unique, however: the behaviour of fish and snails has been analysed for similar purposes. The Russian innovation here is the capacity to judge a small animal’s stress level by measuring its heartbeat.
The head of the Laboratory of Bioelectrical Methods for Ecological Monitoring, Sergei Kholodkevich, was behind the innovation. He invented and patented the method of using large and relatively long-living invertebrates to measure air and water quality.
As well as yabbies, he has used giant African snails to monitor the air quality coming out of sewage-plant incinerators.
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