Researchers find toxic mercury in Vermont vernal pools

SHARON, Vt. (WCAX) New research is finding that some of Vermont's amphibians are growing up with high levels of mercury in their systems.

Steve Faccio knows these vernal pools in the town of Sharon well. "The tadpoles are getting nice and fat," he said. The biologist with the Vermont Center for Ecostudies has been studying the the Upper Valley pools, and the creatures that call them home, for years. "Got a couple salamanders, now I'm hoping to get a wood frog tadpole," he said.

Faccio knows which ones he's looking for and how to swing the net just right to catch them. In just five minutes he's got several small amphibians. "I'm looking at three salamander larva, probably two of them, I think, are Jefferson salamanders and one spotted salamander and then wood frog tadpole," he explained.

Each year, hundreds of young frogs and salamanders will start their lives in these vernal pools as eggs and then develop into larvae, and eventually into adults that will leave the pond and go elsewhere. But while they're in the pools for about three months, they're taking in airborne mercury from coal-fired plants in the Midwest that lands here in the Northeast. Bacteria in these vernal pools are good at turning it into its more dangerous form -- methylmercury.

Faccio was part of the team that collected data from six vernal pools in the Upper Valley in 2015 to track levels of mercury in the critters that live there. They found larva had 20 to 30 times more mercury than eggs did. "This is the stage where the methylmercury in these guys is pretty high, so anything that's dining on these is getting a pretty good dose with each one it eats," he said.

That's not just a problem for the predators who feed on these larva, but their offspring as well. Faccio says they're not sure how the mercury levels affect the larva themselves, but he does know it's a neurotoxin that could affect animals' behavior, or worse. "If it's high enough, it would obviously kill them. So, we don't see mass die-offs and we don't think the levels are high enough that we're seeing that, but there could be behavioral changes that could affect their reproductive success," he said.

The mercury levels were less in adult amphibians. That's likely because they leave the ponds and go elsewhere. But it's not clear how quickly those levels change over time.