Imagine if found that a chemical in our food weakened our resistance to malaria and, when it entered the sewers after we washed it off our dishes, it actually caused mosquitoes to double their egg laying.  We’d call it a perfect storm.

That’s essentially the same situation facing amphibians because of atrazine, as reported in a Scientific American story about Northern Leopard Frogs. According to the story, “the culprit appears to be the common herbicide acting as a double-edged sword: It suppresses the frogs’ immune systems while boosting the population of snails that play host to parasitic worm larvae, the latter of which infect the weakened leopard frogs.”

Another way to explain it, according to the Christian Science Monitor, it this:

Atrazine reduced phytoplankton in the water, making more food and light available for algae. It also appears to speed snail reproduction. The snails, often carrying larvae of parasites harmful to frogs, feed on the increased amounts of algae. Then frogs feast on the snails. In addition, the atrazine deadens the frogs’ immune systems, leaving them less capable of countering the parasites.

Nice to see Joe Mendelson of Zoo Atlanta quoted in the coverage.