By Watershed Protection Program Co-Op Sarah Busby

With their flashy colors, compound eyes, and two sets of wings, dragonflies can be found in abundance, flying around wetlands in the summer months. But hidden behind this charismatic insect lies one of nature’s most successful predators. While hunting prey, dragonflies have a catch rate of 95%, higher than any other animal observed. The secret to their success lies in the many unique adaptations they have accumulated throughout their evolution, including aspects of their eyesight and flight. However, their journey as predators begins well before their aerial emergence at the bottom of our streams. It is here where the dragonfly spends most of its life in its larval, or nymph stage.

Dragonfly nymphs develop in the water anywhere from 2 or 3 months to 1 or 2 years, depending on the species. During this time, nymphs will prey on anything they can catch. Other insect larvae, worms, crustaceans, snails, tadpoles, and even small fish are all fair game for the dragonfly. To catch their prey, dragonfly nymphs have evolved a unique, extendable hinged jaw, or labium, that can shoot out faster than most prey can react. In fact, this creepy arm-like projection is credited as part of the inspiration for H. R. Giger’s Xenomorph design from the movie Alien.

In order to keep up with its prey and avoid predation itself, the dragonfly nymph uses a unique mode of transportation called jet propulsion. No other insect uses such a strategy for locomotion. Nymphs will intake water from their anal valve, extract oxygen from it to breathe, and sharply expel the water back out the anal valve to propel themselves forward. This tri-leaflet valve is surprisingly similar in structure to the human tricuspid heart valve and has even been studied as inspiration for prosthetic heart valve designs.

As they develop, dragonfly nymphs will molt 5 to 14 times until fully grown. As they approach their final larval molt, nymphs will sit in shallow water to prepare, transitioning from breathing water to air. They then emerge from the water, climbing up tall vegetation in the stream or nearby the bank, searching for a nice vantage point to begin their transformation. Here, they will pump and redistribute their body fluids, slowly pushing themselves out of their larval skin. Once emerged, they leave behind an empty cast of this larval skin, or exuvial.

After their extravagant emergence, dragonflies will take off on their maiden flight. A dragonfly’s first flight is typically weak and short lived, making them particularly vulnerable to other predators currently. But as their body and wings harden overtime, they reach their peak predator performance. Once fully developed, dragonflies are ready to take to the skies as masters of flight. With independent control of its fore and hind wings, the highly maneuverable insect can hover and fly in any direction, including backwards.

In addition to their flying skills, dragonflies are equipped with a nervous system working just as fast. They have the ability to fixate on their prey and predict its future location. In this manner, they can intercept prey midair with extreme accuracy. This ability is complemented by their impressive eyesight. Each eye is made up of thousands of units called ommatidia that span across most of the insect’s head. As a result, they have nearly 360-degree vision, with the exception of a small blind spot directly behind them. Their unique vision also serves as a model that multiple researchers are looking to mimic in developing artificial eyes.

The muse of both science fiction and medical invention, these precise predators demonstrate just one of the many treasures our wetlands house. By preserving our wetlands, we ensure that dragonflies can continue to inspire awe and innovation for generations to come.

— By Watershed Protection Program Co-Op Sarah Busby

Sources:

Douglas, E. (2014, July 14). There are aliens among us. The Guardian. Retrieved May 31, 2022, from https://www.theguardian.com/environment/the-northerner/2014/jul/14/burbage-south-yorkshire-aliens-among-us

Evolution, paleontology, and classification. (n.d.). Retrieved June 2, 2022, from https://www.britannica.com/animal/Odonata/Evolution-paleontology-and-classification

Gonzalez-Bellido, P. T., Peng, H., Yang, J., Georgopoulos, A. P., & Olberg, R. M. (2012). Eight pairs of descending visual neurons in the dragonfly give wing motor centers accurate population vector of prey direction. Proceedings of the National Academy of Sciences, 110(2), 696-701. doi:10.1073/pnas.1210489109

Life cycle and biology. British Dragonfly Society. (2022, April 29). Retrieved May 31, 2022, from https://british-dragonflies.org.uk/odonata/life-cycle-and-biology/

Pannett, R. (2015, October 06). Scientists tap dragonfly vision to build a better bionic eye. Retrieved June 2, 2022, from https://www.wsj.com/articles/scientists-tap-dragonfly-vision-to-build-a-better-bionic-eye-1444055235

Perkins, R. (2018, July 17). Dragonfly larvae inspire new designs for prosthetic heart valves. Caltech. Retrieved May 31, 2022, from https://www.caltech.edu/about/news/dragonfly-larvae-inspire-new-designs-prosthetic-heart-valves-82858

By Watershed Protection Program Co-Op Catherine Quinn

Beavers are known and loved as one of North America’s favorite stream architects. With historic removals of these lovely creatures, we are only just now grasping how important they are in shaping our freshwater ecosystems, which encompasses all streams, rivers, lakes, and ponds, as well as the surrounding land. In food chains, removing any level will alter populations of other levels. For instance, if a species of fish is removed from a stream, populations of macro-invertebrates (which are aquatic, typically early development forms of insects) will grow as there are fewer predators to keep their populations in check. In turn, with large numbers of macro-invertebrates, algae will decrease in population size as there is a higher demand for them as food.

With beavers, their impact extends beyond these food chain alterations when they are introduced to a new stream ecosystem. As ecosystem engineers, beavers actively change the physical features of freshwater environments by building their dams. Even failed or abandoned dams continue to affect the environment. Dams are incredibly capable of storing nutrients and groundwater. They affect water flow to varying degrees and can alter water temperatures. These alterations of physical qualities change the quality of life for other organisms. For example, certain organisms rely on food flowing straight into their mouth, habitat, or home and therefore thrive in fast-flowing areas of water. If that water slows down, they may not be able to survive!

In terms of understanding our streams, we already have a considerable grasp of the macro-invertebrates that inhabit them. Freshwater macro-invertebrates typically live on rocks in fast-flowing environments, like streams. They play an integral role in food chains as they consume much of the plant matter in streams and are an excellent food source for predators, both in water and on land. With the introduction of a significant change to an ecosystem, such as a beaver dam, the conditions macro-invertebrates are used to may be impacted, which will either improve or worsen their ability to survive and reproduce in the environment.

Macro-invertebrates play an important role in regulating nutrients as they enter and leave the water. They are also incredible bioindicators, meaning their presence alone can tell us about the health of the water they are living in. Each macro-invertebrate lies on a scale of pollution tolerance, from sensitive to tolerant. In healthy freshwater systems, we see sensitive groups and a variety of species. This biodiversity tells us that the ecosystem is healthy enough to keep the maximum number of organisms happy. With this application of macro-invertebrates, we can use them to understand how beaver dams are affecting freshwater systems entirely.

The jury is still out on how beaver dams impact the existence of macro-invertebrates, but one thing is certain: beaver dams are indeed affecting them. One study by Clifford et al. (1983), found that in an Alberta, Canada stream, macro-invertebrates increased in both abundance (the number of species) and biodiversity (the variety of species) after the introduction of beavers. The study concluded that sections of the stream flowing from the beaver dam are healthier than sections flowing into the dam. On the other hand, in Utah, Washko et al. (2019) found that beaver ponds (areas completely blocked by beaver dams, creating a pond-like environment) showed lower levels of biodiversity and significantly lower populations of macro-invertebrates. The effects of beaver activity on macro-invertebrates likely depend on a variety of factors. Further research will help us better understand the overall impact beavers have on our waters.

— By Watershed Protection Program Co-Op Catherine Quinn

[1] 

Sources:

Clifford, H. F., Wiley, G. M., & Casey, R. J. (1993). Macroinvertebrates of a beaver-altered

boreal stream of Alberta, Canada, with special reference to the fauna on the dams.

Canadian Journal of Zoology, 71(7), 1439–1447. https://doi.org/10.1139/z93-199

Hood, G. A., McIntosh, A. C. S., & Hvenegaard, G. T. (2021). Ecological Compromise: Can

Alternative Beaver Management Maintain Aquatic Macroinvertebrate Biodiversity?

Wetlands, 41(8), 112. https://doi.org/10.1007/s13157-021-01494-7

Robinson, C. T., Schweizer, P., Larsen, A., Schubert, C. J., & Siebers, A. R. (2020). Beaver

effects on macroinvertebrate assemblages in two streams with contrasting morphology.

Science of The Total Environment, 722, 137899.

Shampain, A. (2017, December). The impact of beaver dams on aquatic macroinvertebrate

communities | WALPA.

macroinvertebrate-communities/

Washko, S., Roper, B., & Atwood, T. B. (2020). Beavers alter stream macroinvertebrate

communities in north-eastern Utah. Freshwater Biology, 65(3), 579–591.

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By Watershed Protection Program Co-Op Catherine Quinn

Wetlands are a critical ecosystem in the protection of our watersheds. But what are wetlands exactly? They are just as they sound — land that is wet. How are they critical? In the realm of watersheds, they have many beneficial roles. For instance, the watershed areas protected by the Willistown Conservation Trust make up the headwaters of the Darby, Crum, and Ridley creeks. Their role as headwaters means they have a significant impact on downstream areas of these creeks.

The wetlands surrounding these headwaters help filter the water feeding into them, which in turn helps reduce flooding and pollution. Sphagnum moss, a characteristic plant of bogs, is unique compared to other land plants because it works like a sponge. When precipitation occurs, vegetation normally acts as a barrier from much of the water reaching the ground. However, sphagnum moss, with its sponge-like abilities, will absorb water from precipitation and release it into the ground below, helping maintain that wetland habitat.

Now, how do wetland ecosystems come to be in the first place? Most can be explained by groundwater! Groundwater is also exactly as it sounds — water that exists in the ground. Groundwater can be explained in more detail by the water table, which is a term used to describe the boundary between soil that is completely wet (below the water table), and soil that can hold more water (above the water table). When the ground’s surface is below the water table boundary, or when the surface-level ground is consistently saturated with water (which can also occur with persistent rain), a wetland ecosystem occurs. It is important to distinguish ecosystems like wetlands versus woodlands from one another, particularly in conservation, because of their varying functions, populations, and dynamics. Within wetlands, there is a further multitude of habitat types.

A common subset of a wetland is a bog. You have likely heard of bogs before, particularly in relation to where cranberries come from. Bogs are characterized by the makeup of their soil. These wetlands have had at least hundreds of years to develop by means of decaying plant matter. Bogs form from plant matter decaying into what we call peat, which is known for its significant amounts of stored carbon, otherwise known as a carbon sink. Carbon sinks are hugely important ecosystems in terms of the global climate. Human-caused climate change is primarily attributed to the amount of carbon dioxide in the atmosphere. The deterioration of carbon sinks is a contributor to this problem; a common example of this is deforestation.

Many wetlands in our region likely contained bogs, which is a discovery made through finding layers of peat. In our conservation efforts, it is incredibly beneficial to understand the ecosystems we are working in as well as we can. For example, bog turtles are the smallest turtle in North America and are critically endangered due to poaching and habitat loss. Being able to identify their habitat is critical to their protection as an individual will know to look out for them.

The Watershed Protection Program had the opportunity to shadow George Gress, a bog turtle pro from the Nature Conservancy, on a bog turtle habitat assessment. We discovered that while many wetlands do not contain the habitat that bog turtles look for, that does not necessarily mean they are not there. In ecology, it is quite difficult, and sometimes impossible, to prove the complete absence of a species, especially when it comes to our smaller friends. In addition to bog turtles and sphagnum moss, bog habitats have several other characterizing species. Another common type of bog plant is sedges. Sedges are grass-like plants that grow in clumps and help provide ideal habitat to bog turtles by allowing for muddy, particularly wetter depressions in the ground.

— By Watershed Protection Program Co-Op Catherine Quinn

Sources:

https://education.nationalgeographic.org/resource/bog
https://www.epa.gov/wetlands/what-wetland
https://www.nature.org/en-us/get-involved/how-to-help/animals-we-protect/bog-turtle/
https://en.wikipedia.org/wiki/Peat
https://en.wikipedia.org/wiki/Sphagnum

Established in 2017 through a generous grant from the William Penn Foundation, the Watershed Protection Program Team has been working to monitor the health of the Ridley, Crum, and Darby Creek Watersheds. One of the main goals of the Watershed Program is to study and understand how human activities on the landscape are connected to the function of local streams.

For this year’s Creek Week, we will be sharing information about bogs and wetlands; beavers and stream insects; dragonflies, freshwater mussels, and a case study of water chemistry in Ridley Creek. Each of these topics is inspired by what we have observed during our time in these beautiful watersheds, and highlight the intricate relationships between our soil, air, and water systems.

This Creek Week is not just online! The Watershed Team will be at Ashbridge Preserve on Thursday, June 23 and Saturday, June 25. We welcome volunteers of all ages and abilities to join us as we work to maintain the Ashbridge Tree Planting area! This planting was generously funded by the PA DCNR, and since 2019, we have planted over 1,200 trees along Ridley Creek within the preserve.

The trees along Ridley Creek help keep the water cool, slow and filter stormwater, keep the banks of the stream stable and provide important food resources to power the base of the stream food chain, which extends far beyond the waterway. The insects that rely on the leaves and branches from the banks go on to feed fish, mammals, and birds. Insects that emerge from waterways over the course of the spring fuel migratory and hatchling songbirds! With insect populations declining across the country, it is critical to understand where these insects live and how we can make sure they have the habitat and food they need to thrive.

As caretakers of the origin, or headwaters, of the Ridley, Crum, and Darby Creek stream systems, we have an opportunity to provide healthy water for everyone downstream of us — humans and wildlife alike! Both Ridley and Crum Creeks are potential drinking water sources for thousands of residents in Delaware County, and we are thrilled to have Aqua, an Essential Utilities Company, as a sponsor for this year’s Creek Week! We hope to see you on Friday, June 24, at our Community Supper Series, where you can learn more about the amazing water resources in our region.

Please enjoy this week-long sampling of lessons from the streams. The aquatic environment is a dramatic, wonderful, and ancient world full of resilience and hope. Each of us in the Watershed Program is thankful for the opportunity to share what we have been learning, and we welcome your curiosity and questions!