Celia Chen, Ph.D.
A new NIEHS-funded study found that immature dragonfly larvae can be used to estimate the amount of mercury present in local fish, amphibians, and birds. The study used data from a national-scale citizen science project that began more than a decade ago.
Researchers compiled data on mercury levels in thousands of larval dragonflies collected from 457 locations across 100 U.S. National Park Service sites between 2009 and 2018. They also examined factors, such as habitat type, that may account for variation in dragonfly mercury concentrations, which were nearly two times higher in habitats with flowing water, like rivers and streams, compared with still water sites like lakes and ponds. The researchers suggested that dragonfly larvae can be used to assess mercury in aquatic food webs, because fish and amphibians from the same locations showed similar levels. These findings were used to develop an index of mercury risk to aquatic ecosystems. The team determined that 56% of the park sites were categorized as moderate hazards and 12% presented high or severe hazards to fish, wildlife, or human health. Resource managers can use this approach to more thoroughly assess the threat mercury may pose to ecosystems.
Collectively, this study demonstrated that dragonfly larvae offer a simple and cost-effective tool for estimating mercury exposure in fish and wildlife. It also provides a successful framework for engaging citizen scientists.
Citation: Eagles-Smith CA, Willacker JJ, Nelson SJ, Flanagan Pritz CM, Krabbenhoft DP, Chen CY, Ackerman JT, Campbell Grant EH, Pilliod DS. 2020. A national-scale assessment of mercury bioaccumulation in United States national parks using dragonfly larvae as biosentinels through a citizen-science framework. Environ Sci Technol 54(14):8779–8790.