The Dragonfly Mercury Project is a nationwide program that pairs scientific efforts to understand mercury pollution risks with citizen engagement and education. Dragonfly larvae serve as indicators of mercury, a toxic pollutant, in aquatic food webs. Click on the map below to find information about mercury levels in dragonfly larvae from sampling sites in participating parks. Project-wide data are available for download from the U.S. Geological Survey Science Base Catalog.
Wildlife risk benchmarks that tell us what dragonfly mercury concentrations mean for the animals that consume them are still in development. Early analyses suggest that dragonfly larvae with mercury concentrations less than about 315 ppb, dry weight are likely to be in the lowest risk category. This proposed benchmark - denoted by the red, dashed, horizontal line in the bar chart - reflects potential toxicological risk to fish and wildlife based on a combination of published effects thresholds and trophic enrichment factor estimates. It is important to note that this benchmark only addresses potential risk to fish or wildlife that directly consume dragonflies and likely underestimates risk to fish-eating fish because of food web biomagnification. Expanding the analysis beyond direct dragonfly consumers would require site-specific information on food web structure and community composition. Please keep these considerations in mind when interpreting environmental health risk.
Last updated: October 2, 2018