By: CJ Chen, Spring 2024 Watershed Team High School Intern

From going out to nature preserves and injecting trees with pesticide, to wading through creeks knee-deep and flipping over rocks to find macroinvertebrates, each week at Willistown brought something new. As a high school intern on the Watershed Protection Program team this spring, I saw how a non-profit conservation group functions and what it’s like to be a real-life scientist. I got to experience field work during monthly sampling days, lab work to process those samples, and the many meetings that facilitate collaboration with the community. I learned that watershed science involves a lot more than just water, it encompasses the many overlapping pieces of environmental studies. 

Through real-world experience, I’ve learned much more than I would have in a traditional classroom setting, preparing me well for my future endeavors as I continue my studies at Haverford College in the fall. Moreover, I was able to apply what I learned at Willistown to an independent project at a local park, in which I completed a study, summarized below. 

The project assesses the water quality of Little Crum Creek that passes through Little Crum Creek Park (est. 1970) in Swarthmore Borough, PA. Little Crum Creek is a small stream beginning in Swarthmore, flowing 3.68 miles¹ before joining  Crum Creek and entering the Delaware River (Map 1a and 1b).

Upstream waterways like Little Crum Creek carry contamination and affect the quality of downstream waters. Thus, Little Crum Creek impacts the health of the Delaware River, a crucial drinking water source for 17 million people across five states. 

Land usage affects the health of the waterways; stream pollution increases as open space diminishes due to land development. The area surrounding Little Crum Creek is heavily developed for retail and residential purposes. Because water cannot soak into the impervious surfaces found in these developed areas–e.g. roadways, parking lots, sidewalks, and rooftops–large volumes of stormwater runoff are channeled through drains, which then end up in streams like Little Crum Creek.

Since 1971, Little Crum Creek has been designated as an impaired stream, meaning it does not fulfill federal water quality standards. Understanding the current health of the creek will allow for further improvements in the stream quality to be made by Friends of Little Crum Creek Park and Swarthmore Borough.

Three complete water tests were conducted from March to May using low-cost Lamotte brand kits. While many parameters were assessed, the most important findings are listed below.

Water temperature influences the ability of salts and oxygen to dissolve in the stream, and many organisms require consistent water temperatures to survive. As rain falls on impervious surfaces like pavement, the water heats up under the sun and channels through drains and sewers into the creek. High temperatures usually reflect that the surrounding landscape has a high percentage of impervious surfaces. In Swarthmore, most of the landscape is heavily developed which is reflected at Little Crum Creek with its elevated water temperatures that exceed acceptable levels established by the state across all three samplings in the park.

Chloride and specific conductivity (SPC) together assess the salt concentration. High concentrations of salts harm aquatic organisms, causing deformities in fish and amphibians and killing sensitive keystone organisms like mussels. Salt most often originates from human activity such as excessive road salting. It was found that Little Crum Creek has a salt issue originating from the unnamed tributary. Further continual study of the elevated salts is needed to determine the exact source in the unnamed tributary.

The high salt levels of Little Crum Creek follow the rising national trend of oversalting roadways. This is seen when the chloride levels found in this study are compared to the water quality data from a 1971 United States Geological Survey (Fig. 1).

These issues may be lessened by planting native streamside vegetation, which will address elevated stream temperature and provide a buffer between the stormwater runoff and the creek. Additionally, reducing road salting in the winter and fertilizing lawns at least 48 hours before rain (if at all), are easy community-led steps to reduce the contamination in Little Crum Creek.

Interested in learning more about Little Crum Creek? Click here to read the full report!

¹McGarity, Arthur. Watershed Assessment of the Lower Crum Creek: Decision Support for a Community-Based Partnership. Swarthmore College, 2001. Web. <https://www.swarthmore.edu/NatSci/watershed/319_Project/Full_319_Report.pdf>.

Calvin Keeys

For hundreds of years, people have been moving to the United States and bringing parts of their culture with them. One effect of this is that wildlife is brought over accidentally or purposely and becomes invasive. Invasive species are non-native organisms that cause damage to a new environment by competing against native species for resources and habitat. Even though it is natural for organisms to enter another environment, this is happening more often now than it has in the past due to human actions such as trade, travel, and climate change.  

Freshwater ecosystems have a greater biodiversity per surface area than marine and terrestrial ecosystems (Havel et al. 2015). Unfortunately, these environments, especially lakes and streams, have been some of the most affected by invasive species and species loss. Most aquatic species cannot move from one body of water to another and have instead been moved by people for reasons such as accidental releases, aquarium releases, and fishermen dumping bait. As people continue to change the environment and weather, many non-native aquatic species are expected to increase their populations because they can survive in different environmental conditions while many native species cannot. Invasive species are also better at handling increased land use from people such as habitat destruction and pollution. Invasive species in aquatic ecosystems and the control of them have cost the United States approximately $7.7 billion USD.

Invasive fish can wipe out native species and cause irreversible damage to their environments, and some of the most notable examples are specific carp species. 

Common carp (Missouri Department of Conservation)

The common carp (Cyprinus carpio) was introduced into the Midwest in the late 1800s primarily as a food fish for growing migrant populations. The popularity of the fish and its ability to live in different water conditions led to the US Commission of Fish and Wildlife stocking carp throughout the country to make up for the declining native fish species that were overfished at the time. Common carp eventually spread to other waters outside of the commission’s control and is now established in rivers and lakes in every state except Alaska. It is an active feeder, disturbing sediments and uprooting plants as it forages. High carp populations can cause a deterioration of water quality and habitat for native fish species under certain conditions, such as smaller water bodies with silty bottoms.

Asian carp species (Tennessee Wildlife Federation)

Asian carp refers to several species of carp: silver (Hypophthalmichthys molitrix), bighead (Hypophthalmichthys nobilis), black (Mylopharyngodon piceus) and grass (Ctenopharyngodon idella) that were introduced in the 1970s to aquaculture ponds and wastewater treatment places in the Southeast to clear weeds and parasites. Asian carp have escaped into the Mississippi River basin by jumping over barriers, intentional release, and through flood events. Asian carp can dominate native fisheries in both abundance and biomass, consuming 5-20 percent of their body weight daily. Their high level of feeding on plankton can outcompete native fish and eliminate the main food source for larval and native planktivorous fish. 

They are continuing to make their way up the Mississippi River and its tributaries, the Missouri River and the Illinois River since they are all connected. The Illinois River is connected to the Great Lakes by the Chicago Sanitary and Ship Canal, a manmade connection. The Great Lakes provide a wide range of habitat types that Asian carp can use for spawning, recruitment and maturation. When not feeding on plankton, Asian carp will eat detritus and root in the bottom of protected embayments and wetlands, which could threaten aquatic vegetation that provides spawning habitat for native fish and breeding areas for native waterfowl. Experts are worried that if these fish get into the Great Lakes, they may negatively affect the area’s $7 billion/year fishing industry. 

There are a few ways that you can prevent the spread of invasive fish. Learn to identify juveniles and adults. If you catch one while fishing, do not release it and instead contact your nearest fish and game agency or the US Fish and Wildlife Service (703-358-2148) as soon as possible. Only use wild-caught bait fish in waters where they came from. With your help, we can stop this problem from getting worse. 

References

“Asian Carp Control | U.S. Department of the Interior.” Doi.gov, Aug. 2018, www.doi.gov/ocl/asian-carp-control-0.

‌“Asian Carp – New York Invasive Species Information.” Nyis.info, 2024, nyis.info/invasive_species/asian-carp/. 

Brown, Kubie. “The American Dream: How Invasive Species Have Created New Fisheries | MeatEater Fishing.” Themeateater.com, MeatEater, 18 Jan. 2023, www.themeateater.com/fish/general/the-american-dream-how-invasive-species-have-created-new-fisheries. 

“Common Carp – Mississippi National River & Recreation Area (U.S. National Park Service).” Nps.gov, 2017, www.nps.gov/miss/learn/nature/ascarp_common.htm. 

Couch, Claire, et al. “Evaluating the Institutional and Ecological Effects of Invasive Species Prevention Policy: A Case Study from the U.S. Fish and Wildlife Service.” Management of Biological Invasions, vol. 14, no. 2, 2023, pp. 269–88, https://doi.org/10.3391/mbi.2023.14.2.06.

Havel, John E., et al. “Aquatic Invasive Species: Challenges for the Future.” Hydrobiologia, vol. 750, no. 1, 2015, pp. 147–70, https://doi.org/10.1007/s10750-014-2166-0.

“History of Common Carp in North America – Mississippi National River & Recreation Area (U.S. National Park Service).” Nps.gov, 2023, www.nps.gov/miss/learn/nature/carphist.htm. 

“Invasive Carp Overview – Mississippi National River & Recreation Area (U.S. National Park Service).” Nps.gov, 2023, www.nps.gov/miss/learn/nature/ascarpover.htm.

‌ Klein, Zachary B., et al. “Suppression of Invasive Fish in the West: Synthesis and Suggestions for Improvement.” North American Journal of Fisheries Management, vol. 43, no. 2, 2023, pp. 369–83, https://doi.org/10.1002/nafm.10827.
Varble, Sarah, and Silvia Secchi. “Human Consumption as an Invasive Species Management Strategy. A Preliminary Assessment of the Marketing Potential of Invasive Asian Carp in the US.” Appetite, vol. 65, 2013, pp. 58–67, https://doi.org/10.1016/j.appet.2013.01.022.

By: Sarah Barker

Parasites have a pretty bad reputation, which is well-deserved in most cases, but did you know that they can actually tell us a lot about ecosystem health? Parasites are creatures that rely on another organism in order to complete their life cycle. An example of a common parasite are mosquitos; these insects require blood from a host animal in order to reproduce. In fact, only female mosquitoes suck up blood, males rely solely on plant nectar for their food source. In aquatic ecosystems parasites are incredibly diverse and abundant; they are also often specific about which host species they will infect. These traits mean that parasites can be used to measure biodiversity in a habitat since the more parasite species are present, the more host species are required to support their populations. It is estimated that for every one “free-living” species on earth there are approximately four parasite species that may use it as a host.

Many parasites actually need multiple different host species in order to complete their life cycle (heteroxenous parasites) and oftentimes they use hosts which live in different habitats, connecting aquatic and terrestrial ecosystems as they mature and reproduce. For example Alaria americana, a type of flatworm which hatches in freshwater, requires three to four different hosts in order to successfully reproduce: a snail, a frog, sometimes a transport host like a snake or a small mammal, and a larger predator mammal like a fox or a dog. This means that the presence of this species or other heteroxenous parasites in a watershed indicates the presence of all of their hosts in the same area; making these multi-host parasites a wonderful barometer for ecosystem diversity. 

Adult Alaria flatworms. (Photo Credit: https://wcvm.usask.ca/learnaboutparasites/parasites/alaria-species.php)

Parasites are also essential in maintaining healthy and well-adapted host species populations. There is evidence to suggest that some parasites like intestinal worms may actually benefit infected hosts by removing toxins from their body and taking them up into their own. But, only strong individuals can withstand the stress of a parasite infection and successfully reproduce. Over time, this leads to a stronger community as weaker individuals are weeded out. Additionally, parasites can modify the physical appearance, behavior, energy levels, and even the gut microbiome of their hosts, creating more differences in the host population for natural selection to act upon and more opportunities for parasites to infect new hosts. Most of these modifications serve multiple functions. For example, when mice are infected with toxoplasmosis, a parasitic microorganism, they no longer show a fear response to cats. As a result, these mice are eaten by cats, which are then consequently infected by toxoplasmosis. Since the mice that are vulnerable to toxoplasmosis are eaten and do not reproduce; only mice that are not as vulnerable or more resilient to infection survive and reproduce. Overall this system drives evolution in the host species, increasing the adaptive fitness of populations undergoing parasitic infections.

Mussel larvae, called glochidia, attached to a fish’s gills. (photo credit: Rachel Mair https://usfwsnortheast.wordpress.com/2017/08/21/mussels-making-moves-for-water-quality/8-freshwater-mussel-glochidia-attached-to-gills-of-a-host-fish-credit-rachel-mair/)

In aquatic systems, freshwater mussels start their lives as parasites. The mussel larvae, called glochidia, are expelled in large clusters by female mussels either into the current or directly into a host fish’s face or gills. These glochidia then hitch a ride by attaching to the gills of their host fish and eventually releasing themselves into the water once the host reaches an ideal location. Freshwater mussels perform many vital functions in an ecosystem including filtering out nutrients from the water and anchoring sediment in place using fibers they produce called byssal threads. Finding a healthy population of freshwater mussels in a water body means that their host fish must also be present in significant enough numbers for glochidia to travel with them. 

Parasites may not be the prettiest or most charismatic critters, but they sure do tell us a lot about the health of our aquatic environments. They can also provide some surprising benefits for individual hosts and the ecosystem as a whole. These anti-heroes serve to remind us that every creature has an important job in their environment, even the worms and micro-organisms we wish we could forget!

By: Daniel Price

Plants are an interesting metric to assess environmental health. The common thought that “green is good” when observing non-developed spaces is natural as the alternative is no green in these hyper-developed areas. However, green is not created equal. Some of the green found in Pennsylvania and throughout the U.S. are known to be invasive. Invasive plants are non-native (not from the region) and well-adapted to outcompete the native plants. These plants are great at spreading rapidly and taking or making more efficient use of the resources plants need (think sunlight, water, nutrients). The presence of invasive plants can negatively affect the living organisms that share the same space, putting more stress on an ecosystem. 

One area greatly affected by invasive plants is the watershed. A watershed encompasses the land in which all the rainfall and snowmelt make its way into smaller waterways, like streams and creeks, to eventually flow into a larger body like a lake or ocean. Simply, it’s where a drop of rain will go after it falls. The drop of rain will eventually evaporate or transpire before once again becoming a drop of rain, completing the water cycle. As an organism that needs water to survive, plants are often found in abundance surrounding streams and rivers. A key area plants inhabit is called the riparian zone. The riparian zone is the land directly next to a body of water. Being next to each other, the riparian zone and the waterway have a unique relationship where the contents of one influence the other. Invasive riparian plants can disrupt the normal relationship between the riparian zone and the waterway. One method invasive plants can disrupt this relationship is by releasing toxins to suppress the growth of other plants or changing the pH of the soil to become too basic or acidic for native species to survive. These plants are known as allelopathic. A common allelopathic plant seen throughout Pennsylvania is garlic mustard (Alliaria petiolata). Garlic mustard is not exclusive to the riparian zone but can often be found inhabiting that space. 

Garlic mustard (Alliaria petiolata)

Other invasives like the Japanese knotweed (Reynoutria japonica) which grows very densely, can alter the amount of sunlight the stream and other plants receive, negatively affecting their health. Invasive plants can often take up and retain water differently than native plants. This can lead to discrepancies in the natural relationship between water and waterways. For example, an invasive plant may not require as much water as a native plant, leading to a greater chance that nutrients enter a waterway via runoff, rather than being absorbed by a plant.  

Japanese knotweed (Reynoutria japonica)

Image from Oklahoma State University

A watershed is a highly connected system where slight changes can largely affect the organisms that inhabit it, including humans. Humans are very much a part of the watershed and need to better understand that the actions taken or not taken, greatly affect the health of that ecosystem. A simple way to help combat the spread of invasive riparian plants is to plant native. Regardless of where you plant invasives, they often find ways to spread to more sensitive areas like the riparian zone. The PA Department of Environmental Protection has released a field guide of common invasive plants, detailing how to identify and potentially control these plants in your local area (see link at bottom). Here at Willistown Conservation Trust, the Stewardship Program holds Stewardship Thursdays, where you can volunteer to help reduce the spread of invasive riparian plants, care for newly planted native trees and shrubs, and help establish healthy habitats in public spaces. With a little bit of work and awareness, the spread of invasive riparian plants can be combated. 

Link for PADEP Field Guide – https://www.dep.state.pa.us/dep/deputate/watermgt/wc/subjects/streamreleaf/Docs/Invasive%20Plants.pdf

By: Ryan Ferguson

It was a dark and stormy night. You just bought a cozy lawn chair to relax in the next day, but when you look outside, you see it getting washed away by the flooding in your backyard! All you can do now is sit in the wet grass, yell at the sky, and wonder how you can fix this flooding issue. Excess stormwater runoff comes from numerous surfaces that block water from passing through them, such as roofs, driveways, sidewalks, and parking lots. In addition to flooding, runoff can lead to various issues such as erosion and the transportation of pollutants like fertilizer, oil, and road salt, which ultimately reach our waterways. 

Luckily, you have come to the right spot to learn about a potential solution! Bioretention basins are a fantastic treatment option for stormwater management. These basins, also known as rain gardens, are depressions in the ground that absorb excess stormwater runoff. Bioretention basins typically consist of native plants on top of a combined soil/sand bed, topped with a layer of mulch. The runoff water will flow into the basin, where it goes through two main scenarios. When runoff water flows into the basin, it first passes through the mulch, which traps larger debris. It then filters through the soil/sand bed, where finer particles and pollutants are captured, and beneficial microorganisms break down contaminants. Some of this filtered water infiltrates into the groundwater. Meanwhile, native plants absorb a portion of the water through their roots, which is crucial for photosynthesis, cooling, and nutrient transport. This process not only supports plant growth but also enhances the basin’s filtration capacity by stabilizing the soil. Thus, bioretention basins effectively filter runoff water while supporting plant life, creating a sustainable system for water management and the local ecosystem. It’s a win-win scenario for everything involved! In addition to reducing stormwater runoff, these basins provide numerous other benefits, including:

        Improving water quality: Bioretention basins offer a variety of pollutant-removal mechanisms. This can include filtration through the vegetation, evaporation, transpiration, and infiltration into the soil. The best basins can remove suspended solids, metals, and nutrients.  Studies show that bioretention areas can remove 75% of phosphorus and nitrogen, 95% of metals, and 90% of organics, bacteria, and sediment. When large amounts of these contaminants enter waterways,  they can produce toxins that harm people, animals, and aquatic life. 

       Improving water quantity: Soaking up the stormwater runoff allows the water to infiltrate into the ground and become groundwater. This keeps our streams and rivers flowing and fills up the groundwater that we eventually clean and drink.  Groundwater is also cleaner and colder than storm water, which strongly benefits stream life.

       Habitat improvement: Using native trees and flowers creates habitats for animals such as birds and insects, especially pollinators. If you build multiple bioretention basins together, the benefits only get better for the inhabitants, and if you do not have space to build a basin, planting even a small space with native plants can benefit local wildlife and waterways! Here are other ways to reduce stormwater runoff and stormwater pollution on your property.     

Appearance: Bioretention basins are very pleasant to look at, like outside the Rushton Conservation Center!

Bioretention basins offer versatile applications across diverse environments, including right here at Rushton Woods Preserve! WCT staff are currently working with ThinkGreen and Meliora to design and install a new basin this year. This project is possible through generous funding from the Pennsylvania Department of Environmental Protection and the Department of Conservation and Natural Resources. This new construction will join the rain garden outside of the Rushton Conservation Center, which works to reduce the stormwater impact from the building and parking lot on the preserve. 

Check out Rushton Woods Preserve when the basin and deck are complete, any day of the week from dusk to dawn!

Interested in making your own rain garden? Check out this website to learn how to make a simple rain garden in your own yard: https://www.bhg.com/gardening/landscaping-projects/landscape-basics/make-a-rain-garden/

Sources

https://www.epa.gov/system/files/documents/2021-11/bmp-bioretention-rain-gardens.pdf

https://www.hamiltontn.gov/pdf/WaterQuality/bmps/9.1rag.pdf

https://www.lakesuperiorstreams.org/stormwater/toolkit/bioretention.html#:~:text=An%20engineered%20soil%20bed%20containing,of%20six%20to%20nine%20inches.

Fact Sheet: Bioretention Areas

https://www.epa.gov/soakuptherain/soak-rain-whats-problem