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Biological Indicators

© Diana Tesky

Harmful substances on the land, in the air and in the water can go unseen and unnoticed. We don't feel or observe anything happening to ourselves from these invisible contaminants, nor do we visibly see them. How do we then determine if there is any danger to ourselves or to others?

We can gain clues about the condition of our environment by observing the plants and animals around us. Some plants and animals show reaction to varying conditions in the environment that we wouldn't even notice. For this reason, they can be used as biological indicators or "bioindicators".

Miners used to carry a canary in a cage into the mine shaft with them. If they hit a pocket of natural gas the canary would pass out before any of the workers would be affected. Observing the bird gave them time to retreat out of the mine before they were in danger.

Likewise, the observation of the types and numbers of different animals can give us clues to the environmental conditions. For example, some fish and invertebrates do much better than others in certain conditions. They may thrive in waters with low oxygen content, an overgrowth of weeds, or abundant algae cover, and eat other plants and animals that also do well in these conditions. Others may do better in clear oxygen-rich waters feeding off of other plants and animals that also do well in these conditions.

The EPA uses bioindicators to determine the cleanliness of a watershed http://www.epa.gov/ceisweb1/ceishome/atl... through observation of the numbers and types of fish and invertebrates that differ in tolerance to pollution.

While fish and aquatic vertebrates are used to determine water pollution, lichens and lichen-feeding moths can be used as bioindicators of air pollution in both a visible way and through measurements. http://www.colostate.edu/Depts/Entomolog...

Sometimes it is difficult to determine what the cause is that results in a visible effect in a group of animals. This was the case when deformed frogs were first being discovered in Minnesota and others areas of the country. http://www.pca.state.mn.us/hot/frogs.html The effect was visible, frogs were deformed in any number of ways, but the cause was uncertain.

Learning to watch for clues of potentially harmful environmental conditions through careful observation of animals could prevent health problems in humans. Although we don't notice the affects in ourselves, children and babies may be suffering greater harm due to their smaller size and vulnerability. If we notice problems arising in animal population, or unusual numbers of certain animals (or lack of animals) we can search out the cause to prevent further harm to the environment around us, and ourselves.

The copyright of the article Biological Indicators in Ecology is owned by Diana Tesky. Permission to republish Biological Indicators in print or online must be granted by the author in writing.