Review: Balayiannis & Balayiannis. (2008). Archives of Environmental Contamination and Toxicology, 55: 462-470.

Written: December 9, 2008

Posted: 12/09/08

Word count: 718

Question: Can honey bees be used as sensors for the environment?

Answer: Yes, to detect pesticides in agricultural ecosystems

We all know the phrase “canary in a coalmine”, and not just because of the old tune that Sting wrote before he left the Police. Miners used to put bird cages in the deep caverns in which they worked as a safety precaution. If toxic fumes would build up while they worked, the canary inhabitants would first succumb to them and die; a dead bird meant danger and to leave the area immediately. While antiquated and inconsiderate (from the birds’ point of view), this is one of the more well-known examples of a ‘bioindicator’, or a living system that can detect something in the environment as to provide us with information that we might not otherwise be able to attain.

Honey bees can forage out from the hive about 4 miles, at least if they’re really desperate. This means that they have access to a huge area. Going back to grade-school geometry (and you thought you’d never use it again!), the area of a circle is pr², with the radius (r) being 4 miles. That means a single colony can cover about 32,000 acres, which is over 50 square miles! In doing so, they often scout and locate any number of floral sources from that area. With 50,000 bees per colony, and roughly half of them actively foraging, that’s a lot of interaction with the local environment.

So it has been suggested that honey bees might serve as effective bioindicators. After all, if they are literally sampling nectar and pollen from such a large area, a single colony might serve as a sink for certain substances that its foragers may inadvertently pick up. But what?

Pesticides. A honey bee colony is a very good reservoir for chemicals that they pick up from the environment. Most are benign, such as those they get from flowers (in fact, these floral odors are what bees use to recognize nestmates from non-nestmates). But human-made chemicals are just as easily incorporated into the colony, and they do so in two main ways. First, lipophilic chemicals are those that “love fat” and are easily incorporated into wax, where they can remain for long periods of time (which is why you regularly replace all of your old, darkened combs, right?!). Second, hydrophyllic chemicals are those that “love water” and are easily dissolved into honey.

It is this second approach that a research team in Greece took to use bees as bioindicators of agricultural pesticides. They took samples of honey from all across the country over two years, noting the types of agricultural crops the beehives were near (such as cotton, citrus, sunflowers, and natural vegetation). They then analyzed the chemical makeup of the honeys using gas chromatography to determine the levels of common pesticides and their derivatives (since many compounds break down over time into known and predictable secondary compounds).

Not surprisingly, the researchers found many different chemicals. In all, they found 0% of the non-agricultural samples tested positive for three main classes of agricultural pesticides, but 84%, 47%, and 44% of the honeys were positive for hives near citrus, cotton, and sunflower fields, respectively. What’s more is that most (74%) of all samples were positive for coumaphos, the active chemical in Checkmite+ used to control varroa mites.

Clearly, honey bees are good bioindicators, and what they’re telling us is not very welcome news. They’re saying that they’re picking up lots of chemicals from their environment, the cumulative effect of which is not very well known. They’re also saying that the primary pollutant is something that we as beekeepers are putting into the hives ourselves. While it may be going too far to suggest that honey bees are nature’s canary in a coalmine (as some have suggested in response to CCD), this approach could be used for some more systematic monitoring of agroecosystems in the future to help protect beekeepers and their bees.

Reference

Balayiannis, G. and P. Balayiannis. (2008). Bee honey as an environmental bioindicator of pesticides’

occurrence in six agricultural areas of Greece. Archives of Environmental Contamination and Toxicology, 55: 462-470.