Amphibians Have One More Thing to Worry about--Mercury
Published:07 Dec.2023 Source:U.S. Geological Survey
The first widescale assessment of methylmercury in adult amphibians in the U.S. to date shows that, in amphibians, this toxic compound is common, widespread and, at least for some, can reach very high levels. The study, "Broad-scale Assessment of Methylmercury in Adult Amphibians," which published today in the journal Environmental Science and Technology, brought together scientists from around the country to test more than 3,200 amphibians representing 14 species from 26 populations.
Often formed by microbes living in water, methylmercury is the most bioavailable form of mercury that is highly toxic to vertebrates. It enters the food web and is hard for animals to get rid of once internal, so it accumulates in animals as they continue to feed, a process scientists call bioaccumulation. The study found a way to understand mercury bioaccumulation for amphibians that can't be sampled--by using dragonfly larvae. Scientists determined that the concentration found in these insects are a good stand-in for estimating the amount of methylmercury bioaccumulation in amphibians.
A recent report by the IUCN showed that habitat loss was the greatest threat to amphibians, but their reliance on aquatic habitats also makes them susceptible to environmental contaminants like mercury. Scientists are only just starting to understand how exposure to contaminants contributes to amphibian population dynamics or how contaminants might interact with other threats, like disease. Part of understanding how exposure contributes to decline is determining how exposure varies, and this study provides the most complete picture to date of variation in methylmercury in amphibians.