Frogs and atrazine

What’s causing amphibian declines? Atrazine exposure? Chytrid fungus? Loss of habitat and climate change? All four elements working synergistically? Science News recently ran an in-depth feature re-examining the risks of atrazine, one of the world’s most widely used agricultural pesticides. In this piece, “Weedkiller in the cross hairs” by veteran science writer Janet Raloff, I learned that the largest U.S. producer of atrazine — Syngenta Crop Protection — is 30 minutes down the road from me, in Greensboro, N.C. Her article tussles with the various angles of whether exposure to atrazine in a laboratory setting can accurately model effects of the chemical upon wild amphibians, but one bit of reporting that  made my heart drop was a USGS map delineating where atrazine was predicted to occur based on watersheds and monitoring data. Check it out:

USGS map modeling atrazine concentrations in stream water, in 2007.

The red areas indicate concentrations exceeding 1.026 micrograms per liter (same as parts per billion measurement). I find it really curious that what appears to be Charlotte is an atrazine hot spot in my state. Why not the Piedmont of N.C., where lots of corn, soy and vegetable farming occurs? Why would it accumulate in an urban area? (Do you know? Comment section is always open…) And I can’t help but wonder why there is no data for the area south of Lake Okeechobee in Florida, where large tracts of sugar cane and vegetable  farms have bled phosphorous and nitrogren into the Glades for years and years. It would not be a huge leap of logic to hypothesize that pesticides too are leaking south in this area.

There is a lot of scientific and anecdotal history to the relationship between atrazine and frogs, and I’m not going to try to recap it here. Just go read Raloff’s article, which covers the studies that do and don’t show a measurable effect upon frogs in terms of chemically castrating males, and upon rats in terms of causing hormonal changes.

But a few days after this article published, Berkeley issued a press release on March 1 stating that research had shown atrazine exposure to “common laboratory frogs” could flip male croakers into females. So demasculizining the amphibians totally gets sidelined when compared to flipping the switch on gender. Even more disturbing, they issued a photo of what they say is a male frog that had been chemically converted to a female MATING with its male sibling; the evolutionarily cursed pair produced fertile offspring — though they were all male, with obvious implications for what this would mean in terms of altering population dynamics if it modeled a wild situation. Raloff followed up with an online post incorporating the new study’s findings into her earlier reporting, and again, I encourage you to read this too. And if right about now you are thinking that this new lab model probably does not mean squat, consider this statement in the release about correlations in field work:

Subsequent studies showed that native leopard frogs (Rana pipiens) collected from atrazine-contaminated streams in the Midwest, including from areas up to 1,000 miles from where atrazine is applied, often had eggs in their testes. And many males had lower testosterone levels than normal females and smaller than normal voice boxes, presumably limiting their ability to call mates.

Where I live, the spring peepers have been calling from water-filled roadside ditches for several weeks, and from flooded bottomland forest and emphemeral pools (of which there are many, because we’ve had such a wet winter). I shudder to think that some of these poor animals have screwed up reproductive bits like eggs in their testes, or that they may be more vulnerable to infectious disease because their immune systems are battered or frayed from atrazine exposure.

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