What is a Bioindicator?

Hey Defenders - do you all know the tale of canaries in the coal mines? Well, for a long period of time, coal miners would bring canaries with them underground, not just as friendly companions, but to function as a bioindicator and know if conditions were unsafe for humans. So what does that mean about what a bioindicator actually is? A bioindicator is any species or group of species (known as an indicator species) that can reveal important information about an environment that we humans cannot find out on our own without the help of that species or specialized tools and technology. So with the canary example, coal miners brought them along to see if the levels of carbon monoxide and methane gas ever became unsafe underground. Canaries have a smaller lung capacity than humans, and the way their lungs work made them vulnerable to these dangerous gases, so the coal miners would know that if the canary was breathing ok, they should be fine too. Bioindicators can also tell us how different pollutants would interact together and how long a problem might have existed, giving us some information that physical and chemical testing actually can't. Animals aren't the only bioindicators though, as the presence or absence of certain plants in an area can give us clues on that environment's health as well. So aside from the canary, what other organisms might be bioindicators?

• Amphibians, especially frogs and toads, are strong bioindicators of the accumulation of pollution. Having permeable skin, these animals absorb toxins right through their skin and the gill membranes of their larva are very sensitive to changes in the environment as well.
• Lichen, organisms that are a composite of algae and fungi, are often found on tree trunks and rocks, so their disappearance in a forest can often indicate changes such as sulfur-based pollutants and high levels of sulfur dioxide.
• Invertebrates, like many insects and mollusks, are often very helpful in indicating water pollution and the effects of human activity in tropical forests.