Biomonitoring: When Animals Help Keep Humans Healthy

Jobs for crawfish

For several years, crawfish have been employed at Vodokanal St. Petersburg. They are used to monitor the quality of the water from the Neva River and also – since 2010 – the quality of treated waste water at the South-Western Wastewater Treatment Plant before it is released in the Gulf of Finland. However, it is actually tougher for a crawfish to be picked out for employment at one of the biomonitoring stations than it would be for you to become a CEO at a fairly large and successful company. The crawfish may not be required to email their resumes, but their employers nevertheless have exacting standards when it comes to the selection process.

After crawfish are caught in the Neva River, they are kept for a while in a quarantine aquarium. Specialists from the St. Petersburg Center of Scientific Research into Ecological Safety of the Russian Academy of Sciences analyze the heartbeat and take samples of blood from the crawfish – hemolymph – for analysis.

These stringent tests are used to weed out individuals with health problems. Next come the psychological tests:  weaklings need not apply for a serious job such as this. When a scientist picks up a crawfish in his hands, it should arch its tail and raise both claws. This is how a crawfish demonstrates that it is ready to defend itself.

Over-sensitive individuals are also rejected. This is why calm, narrow-clawed crawfish are more preferable than the more nervous, broad-clawed ones.

For the same reason, female crawfish are never employed at biomonitoring stations. When hatching roe, they become nervous and sensitive, while male crawfish show signs of stress only when something is wrong with the environment.

Thus, only 10% of all the crawfish caught are suitable for work at Vodokanal at biological monitoring stations that assess water quality.

The crawfish are given a job contract for only one year: the work is too hard for invertebrates that are used to hibernating during winter. In order to keep them awake, the water in their aquariums is pre-heated to 12–14 degrees centigrade. However, it is bad for the health of the crawfish to stay awake all year round, so soon after they are retired and released to their natural environment.

Crawfish work in couples, and scientists try to match pairs of animals according to temperament. For example, a pair of sanguine crawfish will give more precise results than a pair consisting of one choleric and one melancholic crawfish.

Scientists attach fiber-optic sensors recording heartbeat to the shells of the working crawfish. If the water from the Neva River in their aquariums appears to be polluted, crawfish will react within a minute or two. Their heartbeat will double and their stress indicator increases from zero to several thousand units. Dispatchers at Vodokanal receive this warning signal and can react to it in time. Applying traditional water testing methods, chemists can easily determine the source of pollution and the concentration of harmful substances. Fortunately, this has never been necessary.

Mollusks and fish helping out

Crawfish are not the only bioindicators used at Vodokanal St. Petersburg. Goldfish and painter’s mussels are also employed as well. A camera is used to record the patterns of movement of the goldfish: if they change, specialists will know that the water is of poor quality. The same goes for the bivalves which inhabit the Neva River: in the case of any pollution they just close their shells.

A snail’s appreciation of fresh air

Giant African land snails (Achatina Achatina) are experts in monitoring air quality. They can sense the concentration of ammonia and carbon monoxide, if it is twice the safe limit, and sulfides or nitrates according to ten of the occupational exposure limit indexes. For this reason, they are now employed at the South-Western Wastewater Treatment Plant to test the quality of the smoke from sludge incineration. They work the same way as crawfish: sensors that record their heartbeat are attached to their shells.

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