(Facing page) A student from Sabino High School in Arizona searches for dragonfly lar vae at Lily Lake, Rocky Mountain National Park, Colorado. (Above) A classmate of hers searches a net for larvae.
Credit: Copyright National Geographic Society/Karine Aigner
A student measures the length of a larva. The students traveled to the park in August 2012 and sampled dragonfly larvae as part of the National Park Service–National Geo graphic Society “BioBlitz.” A student refers to a field guide for help in identifying dragonfly larvae.
Credit: Copyright National Geographic Society/Karine Aigner
A student refers to a field guide to identify dragonfly larvae at Great Smoky Mountains National Park, Tennessee. Dragonfly larvae are being tested for use as an indicator of mercury contamination in the national parks.
Credit: Ami Riscassi
Both dragonflies and damselflies belong to the order Odonata, “toothed ones,” which includes some of the most ancient and beautiful insects that ever roamed Earth, as well as some of the largest flying invertebrates ever to have lived. Dragon flies belong to the subgroup Anisoptera, and damselflies to the group Zygoptera. Among other differences, the abdomen of the larval dragonfly is shorter and bulkier than that of the damselfly. Odonates are set apart from other aquatic macroinvertebrates by their relatively large size, particularly large eyes, and prehensile mouthparts.
Like their adult counterparts, dragonfly larvae are predatory insects. These voracious eaters maintain a higher position on the food chain than other aquatic insects like mosquito larvae and caddis flies, sometimes even eating small fishes. Organisms near the top of the food chain, such as dragonfly larvae, are more sensitive to environmental pollutants like mercury that both build up (bioaccumulate) and increase in concentration higher on the food chain (biomagnify).
Contaminant exposure can be dangerous for humans and wildlife because of the potential for negative health effects. Mercury, a toxic heavy metal, is a contaminant of particular concern, given its ubiquitous nature and ability to induce neurological and reproductive impairment. Mercury threatens the natural resources and values the National Park Service is charged with protecting.
Although there are natural sources of mercury such as volcanoes, much of the mercury that affects national parks is the result of air pollution, and more specifically coal-burning power plants. Waste incinerators and mining operations are other human-caused sources of mercury. Human activities have increased levels of atmospheric mercury at least three fold over the past 150 years. Mercury has an especially long residence time in the atmosphere, and may arrive in parks from distant places such as Asia. Atmospherically deposited mercury can harm the eco logical integrity of aquatic and terrestrial communities in national parks and the wildlife that depend on them.
Concentrations of mercury in dragonfly larvae could indicate the potential risk for the ecosystem. Similar to the “canary in the coal mine,” dragonfly larvae are sentinel species, or biosentinels. As surrogates for ecosystem health, they can be used to detect the potential risk to humans and wildlife by providing advance warning of a danger.
Levels of mercury in dragonfly larvae can serve as proxies for mercury in fish from the same water body. This has potential implications for organisms higher on the food chain, including fish-eating birds and humans. More than 16 million lake acres (6 million ha) and 1 million river miles (1.6 million km) in the United States are under fish-consumption advisories because of mercury, and 81 percent of all fish-consumption advisories issued by the U.S. Environmental Protection Agency are due to mercury contamination. Fish-consumption advisories for mercury are in effect in all 50 states.
While fish are perhaps the most commonly used indicator for mercury contamination because they occur across a wide geography and provide strong links to human and wildlife health, dragonfly larvae are far easier to collect, and they represent the risk from mercury in fishless ecosystems like shallow ponds, ephemeral pools, and marshes—some of the most productive and ecologically important aquatic habitats. They remain in the pond or stream where they hatched from eggs, giving researchers and managers a clearer picture of mercury risk within the watershed where they are caught.
Dragonfly larvae present an ideal vehicle for researchers and park managers to engage citizen scientists in connecting with the natural world. In addition to connecting people to parks and advancing the educational mission, the scientist-citizen partnership makes dragonfly larvae cost-effective tools for monitoring mercury dynamics across many locations.
Forty-two of 46 participating parks have engaged in sampling to date (fig. 1), from Denali National Park and Preserve (Alaska) and Big Cypress National Pre serve (Florida) to Acadia National Park (Maine) and Golden Gate National Recreation Area (California), collecting more than 800 dragonfly larvae at 60-plus sites. Close to 300 citizen scientists, including students, Youth Conservation Corps, volunteers (VIPs), bug camp attendees, and bioblitz participants, have thus far contributed approximately 1,800 hours of volunteer time.
[Map showing parks participating in the dragonfly mercury study through September 2014, as follows:
Study Sites: Acadia NP, Bandelier NM, Big Bend NP, Big Cypress NPres, Cape Cod NS, Channel Islands NP, Chickasaw NRA, Cuyahoga Valley NP, Denali NP & NPres, Glacier NP, Golden Gate NRA, Grand Portage NM, Great Basin NP, Great Sand Dunes NP & NPres, Great Smoky Mountains NP, Indiana Dunes NL, Jean Lafitte NHP & Pres, John Day Fossil Beds NM, Katmai NP & NPres, Kenilworth Park & Aquatic Gardens, Knife River Indian Villages NHS, Lake Clark NP & NPres, Mammoth Cave NP, Marsh-Billings- Rockefeller NHP, Monocacy NB, Mount Rainier NP, Niobrara NSR, North Cascades NP, Olympic NP, Ozark NSR, Pecos NHP, Pictured Rocks NL, Pu’uhonua o Hōnaunau NHP, Rocky Mountain NP, Saint Croix NSR, Saint-Gaudens NHS, Santa Monica Mountains NRA, Shenandoah NP, Timucuan Ecological & Historic Preserve, Voyageurs NP, Yellowstone NP, Yosemite NP
Future Study Sites: Grand Canyon NP, Montezuma Castle NM, Tuzigoot NM, Prince William Forest Park
Source: NPS Air Resources Division 1 October 2014]
Figure 1. Parks participating in the dragonfly mercury study, 2014. The map background shows measured and interpolated mercury deposition data from 2012, courtesy of the National Atmospheric Deposition Program/Mercury Deposition Network.
Citizen scientists, such as the high school students from Arizona, are collecting dragonfly larvae in at least 50 park units across the nation over five years (2011–2015) for analysis of mercury. The species are being tested as biosentinels, shedding light on the risk of mercury contamination throughout the National Park System. Results indicate that no single water chemistry parameter, landscape variable, or dragonfly characteristic adequately describes the pattern of mercury in dragonfly larvae. However, analyses found that dissolved organic carbon, total mercury in water, and pH are important variables, with some influence exerted by east-west position, topography (e.g., wetlands), and habitat guild. Furthermore, site differences within parks reveal that dragonfly larvae can describe fine-scale differences in mercury risk, which supports the utility of these species as biosentinels.
Other research reveals that mercury in dragonfly larvae was correlated with both mercury in water and mercury in fish in the same water bodies (see the article by Roger Haro on page 70). Resource managers and the public appreciate an understanding of mercury levels in the ecosystem because people (and wildlife) rely on the services a healthy ecosystem provides, such as clean water, fish, and enjoyment of the landscape. Bird lovers visit parks to observe birds, not a lack thereof.
The project Web page (http://www.nature.nps.gov/air/Studies/air_toxics/dragonfly/index.cfm) includes the data, available for use by citizen scientists and parks. Final results will be published in the peer-reviewed literature and incorporated into larger-scale mercury research synthesis efforts.
The student returns with another specimen:
“Is THIS it?!” The bug is big and has huge eyes.
“What’s different about this one?”
“It doesn’t have feathery gills,” she says.
“And the abdomen?”
“Short and bulky,” she continues, “and it ends with three short spines.”
[Dragonfly larva of the family Gomphidae, collected at Hodgdon Pond, Acadia National Park, Maine, 2012. Credit: Sarah Nelson]
From field to lab
She excitedly hands the dragonfly larva to her clean-handed, latex-gloved partner, who carefully places it into a labeled, re sealable zipper storage bag, double-bagged to further prevent contamination. They proceed to identify the sample to family, a determination that is validated in the lab by an odonatologist. Each family maintains a slightly different ecological niche, a vari able that can contribute to differences in mercury concentrations.
The samples are preserved on dry ice in the field, then shipped overnight to labs at the University of Maine, Dartmouth College, or the U.S. Geological Survey, where field notes are validated and the samples are analyzed for mercury. Water and sediment samples are collected at the same sampling sites to inform scientists about the influence of environmental characteristics, including pH, dissolved organic carbon, and wetland coverage.
While searching for odonates, citizen scientists also learn about the great diversity of ponds, pools, and other slow-moving (lentic) aquatic systems. Water skimmers, midges, mosquito larvae, and water boat men are only a handful of other aquatic macroinvertebrates that appear in the sampling nets. Fish, slugs, tadpoles, and baby snapping turtles have also been found, enlightening youth and the public about biodiversity and the influence humans have upon natural systems.
The year is 2011. The NPS director issues a Call to Action in an effort to foster stewardship and engagement in the national parks leading up to the centennial celebration of the National Park Service in 2016. Great Smoky Mountains National Park (North Carolina/Tennessee) agrees to be one of two pilot parks for the citizen scientist study of mercury in dragonfly larvae. A Cherokee High School student yells, “I think I found one!”
About the authors
Colleen Flanagan Pritz (firstname.lastname@example.org) is an ecologist with the NPS Air Resources Division, Lakewood, Colorado. Sarah Nelson is an associate research professor, University of Maine, Orono. Collin Eagles-Smith is a supervisory research ecologist with the U.S. Geological Survey, Corvallis, Oregon.
Local experts identify insect biodiversity in Catoctin Mountain Park
By Becky Loncosky
Catoctin Mountain Park has been expanding its knowledge of the biodiversity of invertebrates in the park through the help of local experts to inventory insects. At just 5,872 acres (2,376 ha) in size, Catoctin is a small park in northern Maryland surrounded by rural and suburban development. The park has been going through environmental changes related to white-tailed deer (Odocoilius virginiana) population reduction, and in 2014 completed the fifth year of reductions as prescribed in its deer management plan/ environmental impact statement. This work has resulted in a decrease in white-tailed deer from 123 to 36 per square mile (319–93/sq km). Park staff are tracking the rate of tree seedling regeneration and have already seen the first signs of recovery.
But herbivores are not the only animals putting pressure on park forests. Pests and diseases also have had a negative impact, changing understory environments. Dog wood anthracnose (Discula destructiva) and hemlock woolly adelgid (Adelges tsugae), respectively, are responsible for the loss of many of the understory dogwoods (Cornus florida) and eastern hemlocks (Tsuga canadensis), which has led to a rise in stream temperatures. The emerald ash borer (Agrilus planipennis) is found within 50 miles of the park, and resource managers expect that ash (Fraxinus) species will soon decline.
As a result of this dynamic environment and in order to document future changes, the park realized it needed to determine what species of invertebrates live in the park. Insect biodiversity could increase as the forest recovers from deer overpopulation, but the only insect groups to have been studied previously in the park are butterflies and moths (Lepidoptera) and stream macroinvertebrates, from 1987 to 2004. We focused on dragonflies and damselflies (Odonata) initially, followed by ground-beetles and other select Coleoptera (Carabidae, Scarabaeidae, Geotrupidae, Trogidae, Tenebrionidae, Silphidae), and finally bees (Apoidea).
The surveys were funded through the regional portion of the Natural Resource Protection Program. Costs ranged from $8,200 to $18,800. We contracted two groups of researchers whom we learned about from staff at other parks in the National Capital Region and from our regional Natural Resource and Science office.
Dragonflies and damselflies
Richard Orr of Mid-Atlantic Invertebrate Field Studies (MAIFS) conducted the survey for dragonflies and damselflies in 2009 and sampled all park wetlands, including Owens Creek, Big Hunting Creek, Lantz Marsh, Round Meadow Lagoon, Sawmill Pond, and Hog Rock Seep. Adults, exuvia (the cast skins of the larvae), and larvae were included in the survey. In total, 28 species of dragonflies and damselflies were found to use park habitats. Two species (southern pygmy clubtail and sable clubtail, figs. 1 and 2) are of conservation importance because of their rarity in Maryland. Data collected from each individual included date, location, and other relevant information and were summarized in a spreadsheet for analysis. In addition, this information was augmented with data from a multiyear survey conducted by the Maryland Department of Natural Resources, which covered all the Catoctin mountains that occur in the state.
[Southern pygmy clubtail (Lanthus vernalis). Credit: Richard Orr]
Figure 1 (above). The southern pygmy club tail (Lanthus vernalis), a dragonfly species, is listed as rare in Maryland but was col lected as part of the dragonfly-damselfly inventory at Catoctin Mountain Park.
Credit: Richard Orr
[Sable clubtail (Gomphus rogersi). Credit: Richard Orr]
Figure 2. The sable clubtail (Gomphus rogersi) is listed as rare, in need of conservation, in Maryland. The nymph form is shown here.
Credit: Richard Orr
The beetle survey was to be focused on wood-boring beetles because of the potential for the loss of so many tree species; however, we were not able to locate a researcher with the needed expertise for this survey. It is difficult to get insect experts to work in our small park. So we contacted researchers at the Smithsonian Institution who directed us to Cynthia Fitzler and John Strazanac. They were interested in doing a ground-beetle survey and had the necessary subject knowledge. This was a fortunate connection, and we used a sole-source contract to secure their involvement.
The researchers collected pitfall trap samples at 15 sites every two weeks for 15 consecutive sampling periods from 5 April to 3 November 2011. Ground-beetles (Carabidae) were the most abundant (3,800 individuals) and species rich (67 species) in six targeted families (fig. 3). Specimens in five other families were identified to species: (1) dung beetles, May and June beetles, and chafers (Scarabaeidae: 17 species collected, 523 individuals); (2) darkling beetles (Tenebrionidae: 8 species, 55 individuals); (3) earth-boring scarab beetles (Geotrupidae: 5 species, 219 individuals); (4) carrion beetles (Silphidae: 5 species, 1,019 individuals); and (5) hide or skin beetles (Trogidae: 1 species, 9 individuals). The researchers assembled a voucher collection that included one of each species of beetle. The final report includes maps of the collecting sites and a species list for each site.
[Chlaenius emarginatus, a Catoctin ground-beetle. Credit: (Inset) Jonh S. Strazanac]
Figure 3 (inset). Chlaenius emarginatus is one of the many ground-beetles inventoried at Catoctin.
For a park of its size, and compared with other surveys in the region, Catoctin Mountain Park has high species richness in ground-dwelling beetles. The researchers collected and identified 103 species in six families. Thus the park’s ground-dwelling species list rose from 11 to 114—a 10- fold increase! This relatively high number of species may be the result of the diversity of the park’s forest communities that are at different stages of succession. Recent natural perturbations, like tornadoes and charcoal logging before Catoctin became a national park, have created a dynamic and spatially heterogeneous forest.
Catoctin personnel enrolled in a bee sampling and online identification class offered by the U.S. Geological Survey and carried out the bee-monitoring transect work in 2008. However, making identifications through online resources proved intractable. So we enlisted researcher Richard Orr (MAIFS), who carried out two additional years of bee surveys in 2012 and 2013. The researchers used bee bowl transects (one day or less sampling), propylene glycol cup transects (continuous sampling), and targeted netting during the survey. Catoctin biologists helped Mr. Orr with the bee transects in 2012 and 2013. We targeted various habitats for sampling, including areas that are heavily impacted by nonnative plants, those that were com posed primarily of native plants, high- and low-elevation sites, and a location that had burned previously. The three sampling methods yielded 3,004 bees, representing 93 species or species groups. Additionally, 42 bee species had not previously been reported from Frederick County; one of the leaf-cutting bees, Stelis nitida, proved to be new for Maryland. Spring woodland native bees are negatively affected by Japanese stiltgrass (Microstegium vimineum) and white-tailed deer, which decrease native plant abundance in the park. The researcher provided the park with collection data in spreadsheet form along with a reference collection of the bee specimens (fig. 4).
[Photo of a collection of pinned insect species contained in a wooden drawer. Credit: NPS Photo]
Figure 4. One of the products of the bee survey was a voucher specimen collection prepared for incorporation into the park’s museum collection. This is one of two drawers prepared in this manner.
Before these surveys Catoctin had next to no information on these three groups of insects. On the original park insect list were only six dragonfly or damselfly species, 11 ground-beetles, and no bees. Now the insect list has been extended from 364 to 588 species, greatly expanding our knowledge of these important insect groups. We are very happy with the products that have come from the surveys, as the species lists and insect collections have already been useful for public outreach and education and will be an important resource in the future when the park con ducts repeat surveys.
About the author
Becky Loncosky is a biologist with Catoctin Mountain Park in Thurmont, Maryland. She can be reached by e-mail at email@example.com.
The Crayfish Corps
By Amy Ruhe
[Cartoon-like illustration of a crayfish and the lettering “Crayfish Corps,” which serves as the program’s logo, Credit: National Park Service]
Valley Creek in Valley Forge National Historical Park is threatened by an invasion of rusty crayfish (Orconectes rusticus). The last 2 miles (3.2 km) of this creek flows through the park to its confluence with the Schuylkill River in front of General Washington’s Headquarters. Historically and ecologically significant, Valley Creek is a state-designated “Exceptional Value Waterway” and Class A Cold-Water Fishery that supports a variety of species, including a naturally reproducing trout population. The rusty crayfish, native to the Ohio River drainage, is an invasive species that was first documented in Pennsylvania in the 1970s. Since its introduction, it has spread into the Delaware, Potomac, Schuylkill, and Susquehanna river water sheds, and in 2008 it found its way into Valley Creek via the Schuylkill River.
Nonnative crayfish are one of the biggest threats to crayfish diversity in North America (Butler et al. 2003), with urbanization and associated habitat destruction also posing a significant threat to Pennsylvania’s native crayfish species (Lieb and Carline 1999, 2000; Butler et al. 2003). Crayfish can make up more than 50% of the invertebrate biomass in streams and rivers and are an important food source for trout and other large fish, transferring energy and nutrients up the food chain (Huryn and Wallace 1987; Momot 1995). Rusty crayfish are highly aggressive, which, combined with their larger body size and voracious appetite, gives them a competitive advantage over Pennsylvania’s native crayfish species. In addition to direct competition for resources, rusty crayfish displace native species from preferred habitat, making native crayfish more susceptible to predators as they move to find unoccupied spaces and diminishing food stuffs. The thicker exoskeleton and aggressive defense posture of the rusty crayfish also make them less vulnerable to fish and other predators than native species (Gar vey et al. 1994). Once established, rusty crayfish can disrupt the entire aquatic ecosystem by eliminating native crayfish species, reducing or eliminating aquatic vegetation, reducing the abundance and diversity of aquatic insect populations, and ultimately affecting predators such as trout.
A 2003 crayfish inventory did not find rusty crayfish in Valley Creek but did document two crayfish species, one of which was a previously undescribed species and a member of a species complex (Cambarus acuminatus) that had not been documented in Pennsylvania. Results from ongoing surveys in the area suggest that the range of the previously undescribed species is likely restricted to Valley Creek and a few nearby streams, and that it is probably native to the state (Lieb et al. 2007b). Additional research is needed to determine whether this crayfish is a new or introduced species; however, if it is a na tive species, it is possibly one of the most threatened aquatic species in Pennsylvania because of its limited range, proximity to urban centers, and nearby populations of rusty crayfish (Lieb et al. 2007a). Based on recommendations from crayfish and aquatic invertebrate specialists, the park decided to manage the crayfish as a new species until additional evidence indicates that it is not native.
Managing the invasion
Following the 2008 discovery of the rusty crayfish in Valley Creek, park staff quickly assessed the extent of the invasion and determined that the initial density of this species was approximately one in every four crayfish sampled. Without quick action the population was likely to explode. Valley Forge National Historical Park is situated as the first line of defense in the 24-square-mile (62 sq km) Valley Creek watershed and, with only a small natural resource staff available to manage the invasion, the park established the Crayfish Corps in 2009 to protect aquatic biodiversity and the potentially new crayfish species. From April to October, volunteers from schools, summer camps, corporate groups, conservation organizations, families, and other park neighbors don hip waders and enter Valley Creek to catch and remove rusty crayfish using only nets and muscle (fig. 1). The park investigated additional suppression methods to help control rusty crayfish in Valley Creek, including chemical treatments, electrical barriers, and trapping. These methods have the potential to control the rusty population but are nonselective, and could significantly impact native crayfish and other nontarget aquatic species. Crayfish Corps is proving to be an effective method to selectively suppress the rusty crayfish population while minimizing impacts to other species.
[Members of the Valley Forge Crayfish Corps remove invasive rusty crayfish from Valley Creek, a state-designated “Exceptional Value Waterway.” Credit: NPS photo]