Bluegills induced increased use of cover in all three species, and use of cover also tended to be higher during the day than at night. Tetragoneuria and Ladona generally occupied microhabitats offering cover, whereas Sympetrum usually occupied exposed locations. Laboratory experiments examined the effects of diel period and bluegills on microhabitat use and foraging success, using Tetragoneuria, Ladona and confamilial Sympetrum semicictum, found in a nearby fishless pond. The two dominant anisopteran species, Tetragoneuria cynosura and Ladona deplanata (Odonata: Libellulidae), both strongly avoided colonizing patches where adult bluegills were present. I experimentally manipulated the presence of adult bluegills ( Lepomis macrochirus) in defaunated patches of littoral substrate in a small pond to test whether colonizing dragonfly larvae would avoid patches containing fish. I conducted field and laboratory experiments to determine whether: 1) dragonfly larvae actively avoid fish, 2) microhabitat use and foraging success of larvae are sensitive to predation risk, and 3) vulnerability of larvae is correlated with microhabitat use. This suggests that species which successfully coexist with fish may exhibit behaviors that minimize their risk of predation. “This work is important because it gives resource managers, policy-makers, scientists and the public information to better understand mercury as it is processed in the environment and its impact on public health and wildlife,” said Ralph Perron, air quality specialist.Dragonfly larvae (Odonata: Anisoptera) are often abundant in shallow freshwater habitats and frequently co-occur with predatory fish, but there is evidence that they are underutilized as prey. ![]() “The site-specific biosentinel approach utilizing dragonfly larvae can provide more robust estimates of risk of mercury contamination,” said Nelson. As mercury travels through the atmosphere, it interacts with various environmental processes, which can differ greatly from site to site. It gets into the air from coal-fired power plants, smoke from burning municipal and medical waste, factories that use mercury and active volcanoes. Mercury is one of the most toxic environmental contaminants and is harmful to both humans and wildlife. “Their mercury levels are well correlated with those in fish, linking dragonflies to both environmental mercury concentrations and potential human exposure pathways, making them an excellent indicator for mercury risk.” “Dragonfly larvae tell us a lot because they exhibit higher concentrations of mercury than most other aquatic insects, they’re found in a variety of habitats and their mercury concentrations cascade up the food chain to fish and other aquatic wildlife,” said Sarah Nelson, director of Research, Appalachian Mountain Club. The forest’s Youth Conservation Corps partnered with the Eastern Region’s Air Quality program and Appalachian Mountain Club to survey dragonfly larvae at Cone Pond in Thornton, New Hampshire, and Mountain Pond, near Jackson. The White Mountain National Forest is participating in the Dragonfly Mercury Project, a national initiative involving monitoring, research, education and public engagement to assess mercury concentrations in dragonfly larvae across the United States. Specifically, the larvae are used to predict mercury concentrations in fish and other aquatic life and ecosystems. ![]() NEW HAMPSHIRE-It’s no wonder dragonflies are a symbol for vision and insight: They can see up to 30 “primary” colors, while we humans see the world through only three colors and dragonfly larvae provide real insights into environmental toxins. ![]() Photo courtesy Connor Piechota, White Mountain National Forest Youth Conservation Corps. ![]() White Mountain National Forest’s Youth Conservation Corp members collect dragonfly larvae from shallow pond sediments.
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