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Still Waters Run Deep – With Plastic: The Pervasive Particles in our Watersheds

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By: DeJenae Smith

Two months ago, if you asked me to define microplastics, I likely would have said “small pieces of plastic”, and little else. It was not until my internship with Willistown Conservation Trust and PolyGone Systems where I was introduced to the wonderfully and terribly complex world of microplastics.


So, what are microplastics? According to NOAA, microplastics are less than five millimeters in length (smaller than the size of a pencil eraser). They come in a variety of shapes and colors, and from a wide range of sources (Figure 1).

Figure 1. Infographic showing the sources of microplastics in our oceans. (The Grove)

There are two subclasses of microplastics: primary and secondary. Primary microplastics are released directly into nature as microparticles (ex: fibers shedding from a t-shirt during laundry day) where secondary microplastics come from larger plastic items breaking down. Because of their size, microplastics are almost invisible to the naked eye, but are everywhere in our environment: our air, soil, and most prevalently – our waters. 

While water is the world’s largest resource, we often take this for granted. Out of all countries, the United States has the highest water footprint per person, using about 2,483 cubic meters of water each year (roughly 1,800 gallons each day). And in nearly all U.S waterways, even in the cleanest Pennsylvania streams, microplastics have been discovered (Map 1).

Map 1. Hydrology map of Pennsylvania’s water bodies and major watersheds. Willistown Conservation Trust is located in the Delaware River Basin and it is where our Watershed team works to study Darby, Crum, and Ridley Creek; each of these creeks drain into the Delaware River. (Pennsylvania Department of Conservation and Natural Resources)

Between October 2021 and May 2022, the PennEnvironment Research & Policy Center sampled from 50 streams in Pennsylvania that were deemed Exceptional Value, High Quality, or Class A Coldwater Trout (meaning that a stream or river is clean, cold, and has many wild trout that naturally live and breed) waters. Scientists from the Academy of Natural Sciences analyzed these water samples, finding microplastics in all 50 water bodies (Map 2, Figure 2).
Map 2. The 50 Pennsylvania rivers and streams that were sampled for microplastics in the study conducted by PennEnvironment Research & Policy Center, in collaboration with local volunteers across the state. From October 2021 to May 2022, more than 300 samples were collected. (PennEnvironment Research & Policy Center)
Figure 2. Photographs of microplastics and fibers found in creek samples by Academy of Natural Science researchers. Images were taken under a microscope, red arrows point to a found microplastic piece or fiber. For scale, each gridline is 0.31 cm apart. A) a microplastic fragment in Connoquenessing Creek, B) a microplastic fiber in Neshaminny Creek, C) a microplastic film piece in Darby Creek, D) multiple microplastic fibers in Codorus Creek. (PennEnvironment Research & Policy Center)

More recently, a study in 2024 from Penn State University at John Heinz National Wildlife Refuge and four watersheds (Kiskiminetas River, Blacklick Creek, Raystown Lake, and Darby Creek) also found microplastics polluting the waters. Despite stark differences in the land use surrounding the studied bodies of water, the researchers were surprised to find no correlation between population density, land use, and high levels of microplastics – contradicting common thought that more people means more microplastics. Microplastics are a problem for everyone, regardless of location.

While research continues documenting microplastics in natural environments, their impacts on human health remains unclear. A recent study on mice found that microplastics can travel to the brain after being consumed, leading to symptoms similar to dementia. Though microplastics have been found in the human body, the long-term health effects are still being studied. 

Despite these potentially worrying findings, there are actions we can take. Reducing plastic use is one of the most effective methods to lessen exposure – swapping to a wood cutting board and refillable glass/metal water bottles – even vacuuming your home more often can help. But, if these kinds of changes aren’t possible right now, not placing plastics in the dishwasher or microwave (even if they are labelled as safe) is just as important. High amounts of heat and radiation can cause plastic items to become unstable and shed into smaller fragments, creating secondary microplastics.

For the water both we and other living creatures use, removing litter, especially near stormwater drains, helps prevent plastic from entering waterways (Figure 3). But, it’s important to emphasize that this work should not be done alone. It is through connection with other people and organizations, and making the effort to advocate for the creation and preservation of environmentally beneficial policies that lasting changes can be made to protect our waters, air, plants, wildlife, and in turn – ourselves and one another.

Figure 3. Stormwater drain marking stickers from the Philadelphia Water Department’s ‘Keep It Clean!’ initiative to remind communities that streets and sewers are connected to our waterways and impact wildlife. The PWD also offers free kits for volunteer groups and organizations to mark local storm drains across the city. (Green Philly)

Funding for this project was awarded through the “Protect Your Drinking Water” grant program, administered by the Pennsylvania Environmental Council with funding from Aqua, an Essential Utilities company.

References

Adkisson, K. (2020, November 9). The Root of Microplastics in Plants | PNNL. Www.pnnl.gov. https://www.pnnl.gov/news-media/root-microplastics-plants

Akbari, E., Powers, L., Shah, T., Suri, R., Jedrusiak, S., Bransky, J., Chen, F., & Andaluri, G. (2024). Microplastics in the Delaware River Estuary: Mapping the Distribution And Modeling Hydrodynamic Transport. Environmental Engineering Science. https://doi.org/10.1089/ees.2024.0041

Australian Museum. (n.d.). Water around the world. The Australian Museum. https://australian.museum/get-involved/citizen-science/streamwatch/water-catchment/streamwatch-water-around-the-world/

Balch, B. (2024, June 27). Microplastics are inside us all. What does that mean for our health? AAMC. https://www.aamc.org/news/microplastics-are-inside-us-all-what-does-mean-our-health

‌Bense, K. (2025, March 24). Microplastics lurk in freshwater environments across Pennsylvania • Pennsylvania Capital-Star. Pennsylvania Capital-Star. https://penncapital-star.com/energy-environment/microplastics-lurk-in-freshwater-environments-across-pennsylvania/

D’Hont, A., Gittenberger, A., Leuven, R. S. E. W., & Hendriks, A. J. (2021). Dropping the microbead: Source and sink related microplastic distribution in the Black Sea and Caspian Sea basins. Marine Pollution Bulletin, 173, 112982. https://doi.org/10.1016/j.marpolbul.2021.112982

Hancher, J. (2021, October 13). Eco-Explainer: How storm drain markers connect our streets to our waterways – Green Philly. Green Philly. https://greenphl.com/water/eco-explainer-how-storm-drain-markers-connect-our-streets-to-our-waterways/

Jutamas Bussarakum, Burgos, W. D., Cohen, S. B., Meter, K. V., Sweetman, J. N., Drohan, P. J., Najjar, R. G., Arriola, J. M., Pankratz, K., Emili, L. A., & Warner, N. R. (2024). Decadal changes in microplastic accumulation in freshwater sediments: Evaluating influencing factors. The Science of the Total Environment, 176619–176619. https://doi.org/10.1016/j.scitotenv.2024.176619

Kye, H., Kim, J., Ju, S., Lee, J., Lim, C., & Yoon, Y. (2023). Microplastics in water systems: A review of their impacts on the environment and their potential hazards. Heliyon, 9(3). https://doi.org/10.1016/j.heliyon.2023.e14359

Lai, C. (2022, July 20). Microplastics in Water: Threats and Solutions. Earth.org. https://earth.org/microplastics-in-water/

Lee, Y., Cho, J., Sohn, J., & Kim, C. (2023). Health Effects of Microplastic exposures: Current Issues and Perspectives in South Korea. Yonsei Medical Journal, 64(5), 301–308. National Library of Medicine. https://doi.org/10.3349/ymj.2023.0048

Microplastics found in Pennsylvania’s cleanest streams. (2022, October 26). PennEnvironment Research & Policy Center. https://environmentamerica.org/pennsylvania/center/resources/microplastics-found-in-pennsylvanias-cleanest-streams/

Microplastics – Philadelphia Water Department. (n.d.). Water.phila.gov. https://water.phila.gov/sustainability/watershed-protection/microplastics/

National Oceanic and Atmospheric Administration. (2024, June 16). What are microplastics? Noaa.gov; National Ocean Service. https://oceanservice.noaa.gov/facts/microplastics.html

Okamoto, K. (2024, June 10). Microplastics Are Everywhere. Here’s How to Avoid Eating Them. The New York Times. https://www.nytimes.com/wirecutter/reviews/how-to-avoid-eating-microplastics/

‌Perch Energy. (2022, September 26). 9 Ways To Reduce Your Microplastic Pollution & Consumption | Perch Energy. Www.perchenergy.com; Perch Energy. https://www.perchenergy.com/blog/lifestyle/reduce-microplastic-pollution-consumption

‌Rebelein, A., Int-Veen, I., Kammann, U., & Scharsack, J. P. (2021). Microplastic fibers — Underestimated threat to aquatic organisms? Science of the Total Environment, 777, 146045. https://doi.org/10.1016/j.scitotenv.2021.146045

Ripon Society. (2015, December). Water, Not Oil, is America’s Most Precious Resource | The Ripon Society. The Ripon Society. https://riponsociety.org/article/water-our-most-precious-resource/

Sliman, K. (2024). Microplastics increasing in freshwater, directly related to plastic production | Penn State University. Psu.edu. https://www.psu.edu/news/research/story/microplastics-increasing-freshwater-directly-related-plastic-production

Welcome to Creek Week 2025!

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By: Lauren McGrath

WCT’s Creek Week is a week-long celebration of the amazing water resources in our region and the incredible life that calls the Ridley, Crum, and Darby Creeks home. Over the next several days, Watershed staff will be posting daily on social media and the WCT blog to share their favorite aspects of water related research.  We start small and get bigger over the course of the week!

The week kicks off with an investigation into one of the most concerning recent contaminants of concern: microplastics. Drexel University Co-op Dejenae Smith is working with WCT and PolyGone Systems to study and remove microplastics from the environment. 

Tuesday and Wednesday bring the fascinating world of biofilms into focus! Sarah Barker, WCT’s Watershed Technician, shares her love of the slimy microscopic world that coats the rocks and floats in the water column beginning with microalgae and diatoms.  This is a two part series that you do not want to miss!

Thursday zooms back out to look at the larger and more easily identified photosynthesizing community that lines waterways: Riparian trees! Dejenae shares what she has been learning through her co-op on how to read the landscape along a waterway and the role that these beautiful native plants play in keeping streams and rivers healthy.

Friday’s blog post features Lauren Carroll, a high school senior from Conestoga High School, who shadowed the Watershed Protection Program over the month of May. Lauren is interested in a career in chemistry, and had the opportunity to help WCT understand how water chemistry changes in a stream, and how that experience may have changed her view of future careers in a positive way!

Creek Week wraps up with a love letter to one of the rarest stream residents in Ridley Creek: the American river otter. An otter was spotted in Ridley Creek in December 2023, and this blog looks into why seeing this elusive watershed resident is such big news that we are still excited about it. 

Along with all of the virtual education this week, the Watershed Protection Program team is also excited to get into Ridley Creek with you! Join us on Wednesday, June 11 at Ashbridge Preserve to Uncover Living Clues to Stream Health! On Thursday, June 12, you can spend the morning working side by side with Watershed and Stewardship staff for Stewardship Thursday, also at Ashbridge Preserve.  If a weekday morning does not work for your schedule, never fear! Watershed will also be out at Ashbridge Preserve on Saturday, June 14.

Thank you for joining WCT this week and wherever you are joining us from, we hope that you can take some time to connect with the incredible and resilient natural world!

Funding for this project was awarded through the “Protect Your Drinking Water” grant program, administered by the Pennsylvania Environmental Council with funding from Aqua, an Essential Utilities company.

Beavers return to Ashbridge Preserve

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By: Watershed Program Staff

The first telltale signs of beaver (Castor canadensis) activity at Ashbridge Preserve, found in late October, were chewed branches and a suspicious build up of twigs, branches, and other woody debris in Ridley Creek. Soon after, Watershed Program staff noted a slow, but steady, increase in the water depth in the riparian restoration area which could only mean one thing: the beavers had arrived in Ashbridge Preserve! Over the course of the next several months, beaver constructed four dams within Ashbridge Preserve, raising water levels throughout Ridley Creek.

The largest dam, visible upstream from [1] the stepping stone crossing, was the perfect candidate to place a game camera to watch the construction process. Almost immediately, the cameras picked up footage of a single large beaver, working tirelessly each night to build and repair the dam. Within the first several weeks, a second smaller beaver joined in the effort, carrying small twigs and branches, gently patting mud and leaves into the construction project, and generally getting in the way as all children do while learning how to help their parents. They worked together most nights to create a system of dams that have had a big impact on Ridley Creek during the driest fall in Pennsylvania history.

At the beginning of October, water depth in the riparian restoration area in Ashbridge Preserve had fallen to the lowest levels recorded on the EnviroDIY Sensor. No rain fell during the month of October, yet the EnviroDIY Sensor recorded a four-fold increase in water depth as a result of the construction of beaver dams in downstream sections of the creek (figure 1). A beaver’s dam building behavior can completely change an ecosystem: flooding forests, creating ponds, irrigating desiccated soils, and bringing life with each trickle of water. Beaver ponds that form upstream of a dam slow the rate of flowing water and flood the surrounding watershed area. This allows moisture to permeate more soil as the water level rises. As semi-aquatic herbivores, beavers live both on land and in water, and the engineering of higher water levels through the construction of dams provide easier access to food and less risk of predation, especially for young family groups. In periods of drought, like that which impacted the region in October, the increasing water level provides essential hydration for thirsty plant roots while also creating important refuges for aquatic and terrestrial wildlife alike.

Where beavers are active on the landscape, there is an increase in ecosystem biodiversity, wildlife abundance, and improved water quality. When beavers build dams, the ponding leads to more water entering the subterranean aquifer, which provides a critical resource during periods of low rainfall. Increased water retention supports environmental resilience, with hydrated soils and vegetation being more resistant to wildfires, storms, and erosion, and providing a safe haven for wildlife. While there is no guarantee that the family of beavers who called Ashbridge Preserve home this past winter will stay through the spring, the impact that they have had on the watershed will be long lasting.

Figure 1. EnviroDIY Sensor Station water depth in Ridley Creek from September to December 2024. The blue line demonstrates the impact of beaver dam construction in Ridley Creek at Ashbridge Preserve. The black line shows water depth in Ridley Creek during the same period where beavers are not present. Water depth at Ashbridge Preserve increased from 106 mm to 402 mm while the downstream site logged no increase. Spikes in water depth are from small rainstorms during this period.

Busy Beavers Revive Thirsty Landscapes

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How the American Beaver Mitigates Drought Impact

By: Sarah Barker

As we near the end of what is shaping up to be the hottest year in documented history, one of nature’s most impactful (and adorable) engineers is working hard to keep our ecosystems green. The American beaver (Castor canadensis) may be our saving grace as drought and wildfires become more frequent due to the growing climate crisis. Research conducted over the past few decades reveals the profound positive influence beavers have on their habitats across the country, even in extreme conditions. Whether they are meandering through Pennsylvania temperate forests (Margolis et al., 2001), arid landscapes in Nevada (Fairfax & Small, 2018), or habitats west of the Rockies (Fairfax & Whittle, 2020), the importance of beaver activity in building environmental resilience cannot be ignored.

Beavers are herbivorous and semiaquatic mammals, they eat woody vegetation, fruits, and herbaceous plants like skunk cabbage or sedges, and they live both on land and in the water. Beavers are renowned in the animal kingdom for their impressive constructions made from chewed trees, shrubs, and miscellaneous found materials. While large dams may be their calling card, they also build homes called lodges into the banks of water bodies, food caches to sustain them through the winter, and trails and canals for transporting food and building materials.

Game camera footage of two beavers adding sticks to one of their dams at Ashbridge Preserve.

Before the European settlement of North America, beavers could be found in nearly every freshwater body in the country. As colonization spread from coast to coast, beaver populations dwindled as they were hunted to near extinction due to their value in the fur trade, significantly altering ecosystems. Beavers have since reclaimed much of their historical range thanks to nationwide conservation and reintroduction efforts, allowing these master craftsmen to once again shape the landscape. Evidence suggests we all stand to benefit greatly from their return. 

Beaver dams can completely change an ecosystem: flooding forests, creating ponds, irrigating desiccated soils, and bringing life with each trickle of water. Beaver ponds that form between dams or upstream of a dam slow the rate of flowing water and flood the surrounding watershed area. This allows moisture to permeate more soil as the water level rises. In periods of drought, like we have experienced in PA over the past few months, this increasing water level provides essential hydration for thirsty roots. It also creates important refuges and oases for aquatic and terrestrial wildlife alike; including fish, frogs, turtles, raccoons, mink, deer, and more. Birds too can be observed bathing in beaver ponds and hunting for fish or insects.
A recently constructed dam created a beaver pond upstream at Ashbridge Preserve.

By building successive dams in the same stretch of a river or stream, beavers can sustain or create wetlands even during intense drought; a behavior we have observed at WCT’s Ashbridge Preserve! Beavers are slow and clumsy on land but are graceful swimmers. Therefore, higher water levels provide easier access to food and less risk of predation. Beavers are also fantastic stewards! They chew down local invasive plants like privet and grapevine for their dams while selectively foraging twigs from natives like black willow or red osier dogwood so that they may produce many more shoots in the following growing seasons. This behavior helps maintain native plant populations as invasive species become increasingly common.

Beaver chew on a Dogwood tree at Ashbridge Preserve.

These benefits increase ecosystem biodiversity, organism abundance, and water quality with the impact being so significant that it can be observed by NASA satellites! Green can be seen spreading outward from beaver dams into the surrounding floodplains while other areas without beaver activity wilt under extreme conditions. A study based in Nevada found that in areas where beaver dams had been established, the rate of water evaporation was significantly lower compared to environments lacking beaver activity (Fairfax & Small, 2018). This means that water stays in the ecosystem for longer, and during drought this is critical. Increased water retention supports environmental resilience, with hydrated soils and vegetation being more resistant to wildfires, storms, and erosion, and providing more favorable conditions for wildlife. Depending on the region, increased water level and retention can also allow for the dilution of concentrated salts and nutrients, providing more time for them to be absorbed and broken down, lessening their impact on the environment as a result.

Satellite image of a study area in Idaho showing the impact of Beaver activity on large-scale plant growth. Blue regions represent dense canopy coverage. (Photo credit: NASA)

As temperatures continue to rise with each passing year and the weather becomes increasingly unpredictable, these friendly rodents provide fortification and solace for wildlife and humans alike. While they may have a historical reputation as a nuisance, their beneficial environmental impacts are undeniable. Beavers are our allies in the fight to protect and remediate our environment and they sure do look cute doing it!

References:

Dewey, C., Fox, P. M., Bouskill, N. J., Dwivedi, D., Nico, P., & Fendorf, S. (2022). Beaver dams 

overshadow climate extremes in controlling riparian hydrology and water quality. Nature 

Communications, 13(1). https://doi.org/10.1038/s41467-022-34022-0 

Fairfax, E., & Small, E. E. (2018). Using remote sensing to assess the impact of beaver damming 

on riparian evapotranspiration in an arid landscape. Ecohydrology, 11(7). 

https://doi.org/10.1002/eco.1993

Fairfax, E., & Whittle, A. (2020). Smokey the Beaver: Beaver‐dammed riparian corridors stay 

green during wildfire throughout the Western United States. Ecological 

Applications, 30(8). https://doi.org/10.1002/eap.2225 

Hood, G. A., & Bayley, S. E. (2008). Beaver (Castor canadensis) mitigate the effects of climate 

on the area of open water in boreal wetlands in Western Canada. Biological 

Conservation, 141(2), 556–567. https://doi.org/10.1016/j.biocon.2007.12.003 

Margolis, B. E., Castro, M. S., & Raesly, R. L. (2001). The impact of Beaver Impoundments on 

the Water Chemistry of two Appalachian streams. Canadian Journal of Fisheries and 

Aquatic Sciences, 58(11), 2271–2283. https://doi.org/10.1139/f01-166 

NASA. (n.d.). NASA data helps Beavers build back streams. NASA. 

https://spinoff.nasa.gov/Beavers_Build_Back_Streams

Rosell, F., & Campbell-Palmer, R. (2022). Beavers: Ecology, behaviour, conservation, and 

Management. Oxford University Press. 

Hot, Dry and Salty: The Impact of Droughts on Freshwater Systems

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By: Lauren McGrath, Director of Watershed Protection Program

For the Watershed Program, it has felt like the September that never ends. A warm, dry autumn has made for great foliage, but there are growing concerns about the impact of a fall with no rain. Fall of 2024 has been notably dry, with Philadelphia having the longest dry period since weather record-keeping began 153 years ago – an unbelievable 42 days with no rain. For the first time in the region, there was no rain in October, and temperatures were unseasonably warm, which can cause more water to leave the soil. While the dry period ended with rain on November 8, Chester County is still facing drought conditions expected to persist throughout the month of November. 

With this record-breaking dry spell, what is the impact on local streams?

Unsurprisingly, the lack of rain has a significant impact on the health of local waterways. As rain continues to be elusive in the region, the amount of flowing water in many waterways continues to drop causing physical changes to stream habitat. Low flow conditions can cause dramatic changes to resource availability. The resulting changes to the flow patterns and currents can cause sections of normally flowing streams to become isolated and turn into pools, trapping wildlife in stagnant water. Decreased water levels also means that there is just less space for wildlife in the stream, causing crowding and more competition for fewer resources. In some cases, small streams can dry up entirely. This dramatic loss of habitat has been documented at one site in the Darby Creek Watershed already during this historic drought. 

Droughts also cause changes in water chemistry. With flow patterns changing, the availability of oxygen can be reduced, with slow-moving water failing to distribute dissolved oxygen at levels to support sensitive stream life. This can create life threatening conditions for sensitive stream life. Changes in flow also influence chloride levels. While some chloride is present in the geology of Chester and Delaware Counties, the majority of chloride is introduced into local watersheds through the application of road salts (usually sodium chloride, NaCl) to melt snow and ice in the winter. As the snow and ice melt, the salt flushes into local waterways. In areas where salt is applied frequently and in abundance, the chloride can build up in the soils, leading to salty groundwater and high levels of chloride year round – instead of just after winter storms.  Chloride, including that from road salt, is known to be harmful to sensitive fish and invertebrates in freshwater systems.When salt buildup in soils meets drought conditions, it leads to salty streams. Less rainfall, (or in the case of October 2024 no rainfall), leads to little to no dilution of groundwater entering the stream, increasing the concentration of chloride in local waterways. When these dry conditions are paired with unseasonably warm temperatures (Fig. 1), it is a recipe for rapid evaporation of surface waters (Fig. 2). Evaporation leaves chloride behind, causing even higher concentrations of chloride ions.  During a severe drought, stream systems are almost entirely fed by groundwater, which means the potential for higher concentrations of chloride ions.

Figure 1. Historic Air Temperature changes for Pennsylvania. This map shows the average maximum daily temperature for October 12, 2024 through November 11, 2024 compared to the historical average (1991–2020) for the same 30 days. Map provided by Drought.gov.
Figure 2. Soil moisture levels in Southeastern Pennsylvania as of November 14, 2024. The entirety of the region is under severe drought conditions and facing extremely dry soil conditions. This NASA SPoRT-LIS soil moisture map shows the moisture content of the top 100 cm of soil compared to historical conditions (1981–2013). Map provided by Drought.gov.

Salty streams become extremely dangerous for sensitive aquatic life as temperatures rise, with both chloride and warm streams causing stressful conditions for stream residents. With unseasonably warm days still to come in November and no rain in the forecast, there is likely to be a long-term impact on the health of local streams. Warm air temperatures also mean less oxygen available in the water, increasing the risk factor for aquatic life.

While the drought is not necessarily caused exclusively by climate change, it is being made more severe by the warm temperatures, especially in the fall months of September and October. Models predict that these months will continue to warm at a faster rate than the rest of the year and rainfall events will be extreme, with more rain falling in shorter periods of time. The Watershed Team monitors water temperature, conductivity, and chloride levels at ten sites across Ridley, Crum, and Darby Creeks as well as an additional 34 sites throughout the Darby and Cobbs watershed through the Darby & Cobbs Creek Community Science Monitoring Program on a monthly basis. As data analysis takes place, we will share updates on what we are learning and how you can help stream health.