By: DeJenae Smith

If you want insight on the health of a body of water, having a laboratory or expensive equipment is not a necessity. Often, all you have to do is look up – not at the sky or its clouds, but at the trees. Unlike migrating birds, fish, or other highly mobile organisms, trees stay rooted in one place, living alongside or near a stream, creek, or river for as long as the water flows, and often for many centuries after. Their presence, structure, and diversity can offer powerful information about the health of a watershed.

Over the past few months that I’ve spent as a Drexel University co-op with WCT, I have learned a lot about the process of ‘reading the landscape’ and its value; and I quickly realized how much of that understanding depends on trees.

While trees serve many functions for an ecosystem and planting more in a space is beneficial, it is important to plant a tree in the appropriate conditions to increase their chances of survival. As I’ve walked through Kirkwood and Ashbridge Preserves and participated in riparian tree plantings, I have learned from my mentors about three key “zones” for trees and shrubs as it relates to wetlands.
Zone 1 is located closest to the stream’s edge. Examples of trees WCT has planted here are silver maple (Acer saccharinum), buttonbush (Cephalanthus occidentalis), American sycamore (Platanus occidentalis), and swamp white oak (Quercus bicolor) (Figure 1). These species are very tolerant to wet soils and are key in keeping a stream bank together (Figure 2).

Alongside structural support, trees in Zone 1 provide other functions. As they grow and create canopies, they provide shade over a water body, keeping the water cool for fish and invertebrates. Trees are also capable of cladoptosis, the process of shedding their branches. When branches fall into water, they can provide habitat, hiding places, or transportation for small aquatic organisms (Figure 3).

Going even further, Zone 3 is located about 50 feet from the water, typically contains fewer large trees and is full of native grasses, shrubs, and wildflowers. Plants in Zone 3 are the first line of protection for the stream, filtering runoff that may carry sediment, nutrients, or pesticides. Zone 3 also helps prevent flooding. When there’s heavy rain,  stormwater can rush into a watershed at once. Dense vegetation in Zone 3 slows that water before it reaches lower zones. As water takes longer to travel, more of it soaks into the soil and helps refill the groundwater supply. 

Groundwater is essential for drinking, farming, and keeping land stable. If too much is removed, the ground can sink – a problem called subsidence. Zone 3 plants help prevent this by allowing rainwater to seep into the ground. Some of the shrubs WCT has added here include red osier dogwood (Cornus sericea), witch hazel (Hamamelis virginiana), and common ninebark (Physocarpus opulifolius).

Each layer of the riparian zone plays a unique and vital role in keeping our watersheds healthy. While these areas may seem like simple scenery, the trees, shrubs, and plants that grow there work hard to stabilize streambanks, filter pollutants, support wildlife, and show us the health of our watersheds. Learning to read these green spaces during my time with WCT has deepened my appreciation for the overlooked power of riparian zones and the trees that stand not in stillness, but in silent service to the land and its ecosystems.

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

‌Multifunctional Riparian Forest Buffers: More Than Just Trees. (n.d.). Extension.psu.edu. https://extension.psu.edu/multifunctional-riparian-forest-buffers-more-than-just-trees

‌Penn State Extension. (2005, February 11). Riparian Buffers for Wildlife. Penn State Extension. https://extension.psu.edu/riparian-buffers-for-wildlife

Plant Materials | Natural Resources Conservation Service. (2024, March 7). Www.nrcs.usda.gov. https://www.nrcs.usda.gov/plant-materials

Riparian Tree Plantings – Western Pennsylvania Conservancy. (2023, October 20). Western Pennsylvania Conservancy. https://waterlandlife.org/trees/riparian-tree-plantings/

‌Trees, Shrubs, and Groundcovers Tolerant of Wet Sites. (2022). Psu.edu. https://extension.psu.edu/trees-shrubs-and-groundcovers-tolerant-of-wet-sites‌US Department of Commerce, National Oceanic and Atmospheric Administration. (2019). What is subsidence? Noaa.gov. https://oceanservice.noaa.gov/facts/subsidence.html

By: Sarah Barker

You may have heard about algae – most likely in the context of its classification as an aquarium nuisance or as giant swaying ropes of kelp in the ocean. However, it is not an understatement to say that they may just be the single most important part of freshwater ecosystems. Algae encompass an incredibly diverse group of photosynthetic plants which may be found in any place where water is present; including but not limited to ponds, streams, marshes, cracks in building facades, storm water drainage, and even growing on animals! Algae can be large and obvious in a creek, branching out and forming great tufts of emerald green or it can be quite secretive and tiny, colonizing stones and silty stream banks with an inconspicuous yellow-brown film. The most impactful of these varied organisms are often the most overlooked (literally) – microalgae. Microalgae are species of algae which are only visible under magnification. They form communities either attached to a substrate like stones or plants (called benthic) or unattached and freely floating in the water column (called pelagic or planktonic).

Microalgae are powerhouses of energy production, nutrient cycling, and water filtration for the entire stream ecosystem. They generate energy through photosynthesis during the day which is transferred up the food chain as they are eaten by insects which are then eaten by birds or fish which may then be eaten by a person! They also capture and break down harmful pollutants both organic like nitrogen or phosphorus, and inorganic like heavy metals or pesticides. Microalgae are also fantastic carbon transformers; they take carbon dioxide from the water and convert it into less harmful carbon molecules which can then be stored inside their cells or used by other creatures. This process captures carbon that might otherwise be added to the atmosphere and instead stores it safely preventing that carbon from contributing to climate change.

There are a few major groups of microalgae that are especially critical in stream habitats: diatoms, green algae, euglenoids, and cyanobacteria. Each of these members have unique adaptations and each form associations with other kinds of microalgae, bacteria, aquatic fungi, and viruses within the water column causing robust communities of microbes to join chemical forces. These communities are called biofilms and almost always require several different kinds of microbes to function effectively. Biofilms are a mini city in their own right, but the microalgae are the energy grid. These remarkable microbes, diatoms in particular, form complex beneficial relationships with their bacterial neighbors to trade molecules and take advantage of every community member’s strengths. Just as a human community may trade eggs for lavender or tools for cloth, microalgae trade dissolved carbon that they are unable to further break down in return for nutrients and minerals that bacteria are able to process for them. This kind of equally beneficial relationship is called mutualism and is a strategy as widespread in nature as the microbes themselves!

Microalgae embody a very valuable lesson – that true strength comes from community and reciprocity. In order to survive they rely upon products supplied by other organisms: chemicals produced by their bacterial neighbors, and carbon dioxide exhaled by animals. However, in exchange they provide essential oxygen, lower the acidity of the water, break down dangerous contaminants, and act as food for countless grazing stream life. Microalgae are also quite resilient to disturbances and recover from floods quickly, often colonizing habitats where other organisms cannot survive and fixing them up into a once again livable home. All of these wonderful traits are possible through relationships, showing once more how real power lies in connection. Essential support can arrive from even the most unexpected and undervalued places, even scum covered streambeds. When times are rough and the number of trials outweighs the number of celebrations, remember the microalgae filtering polluted water; performing a difficult job that nobody else wants to do for the benefit of all other life downstream. None of us are truly alone – we stand on the shoulders of giants and microbes alike!

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:

Peterson, C. G., Daley, A. D., Pechauer, S. M., Kalscheur, K. N., Sullivan, M. J., Kufta, S. L.,  Rojas, M., Gray, K. A., & Kelly, J. J. (2011). Development of associations between  microalgae and denitrifying bacteria in streams of contrasting anthropogenic influence. 

FEMS Microbiology Ecology, 77(3), 477–492.

https://doi.org/10.1111/j.1574-6941.2011.01131.x

Stevenson, R. J., Bothwell, M. L., & Lowe, R. L. (2008). Algal ecology: Freshwater benthic ecosystems. Academic Press. 

Yao, S., Lyu, S., An, Y., Lu, J., Gjermansen, C., & Schramm, A. (2018). Microalgae-bacteria symbiosis in microalgal growth and biofuel production: A Review. Journal of Applied Microbiology, 126(2), 359–368. https://doi.org/10.1111/jam.14095

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).

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).

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.

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

By: Sarah Barker

Rivers and streams are very dynamic, changing physically and chemically with every passing minute. Erosion, the process of sediment wearing away over time, plays an essential role in this endless shaping and reshaping. The movement of sediment in freshwater systems is incredibly important for water quality and habitat health. Soil binds to nutrients and salts, trapping them and preventing them from washing into streams. When severe weather events or abnormal conditions carry away large amounts of sediment these pollutants are freed into the water column, impacting wildlife and drinking water. The rate of erosion is also heavily influenced by the amount of development in the surrounding watershed. As land around a stream is developed, runoff increases and erosion worsens.

Often, erosion is considered as a consequence of storms. However, in humid, temperate climate regions like Southeastern Pennsylvania, the most influential form of erosion actually occurs in the winter, called freeze-thaw erosion. This type of erosion happens in natural cycles when extreme differences in temperature, from below freezing to above freezing, occur over a short period of time. As water freezes in the soil it expands, loosening soil particles, when it warms up suddenly after a cold spell this ice melts, creating space between particles and causing them to wear away more quickly. The impact of freeze-thaw erosion worsens after winter rain as the flow of water over already weakened banks accelerates soil loss. Development near water only makes the issue worse, providing hardened surfaces for runoff to speed into flowing water like a race track, bringing more and more loosened soil down with it. It is projected that these freeze-thaw cycles will only increase as climate change continues to modify normal weather patterns towards extremes.

Erosion on the side of a stream bank in Darby Creek.

There are other factors that can contribute to the severity and frequency of freeze-thaw cycles as well. One of the most important is the presence of vegetation along stream banks. Roots hold soil together, slowing erosion in general, however, the density of plants matter too! A 2006 study found that dense plant cover insulates banks from extreme temperature shifts over the course of a day, protecting soil from more frequent freeze-thaw cycles. Stretches of bank without dense canopy or understory were much more vulnerable to daily changes in temperature and experienced as many as four times the number of freeze-thaw cycles as densely planted sections (Wynn & Mostaghimi, 2006).

The local geology and predominant soil type of a region also significantly influence the impact of freeze-thaw erosion. Fine sediment types like clay, silt, or loam tend to be much more susceptible to this process than coarser varieties. In addition, the Piedmont region of Southeastern Pennsylvania is more heavily impacted compared to other kinds of regional geology, like the Atlantic Plain (Inamdar et al., 2018). At Rushton Woods Preserve, an ongoing erosion study documenting the progressive changes within an erosion feature called a headcut may show just how severe freeze-thaw cycles can be when these factors combine. 

Starting in June 2024, 40 pieces of  rebar, called erosion pins, were hammered into the sides of a headcut at Rushton Woods Preserve to measure the rate of soil movement due to erosion. The study area is mostly fine sediment under a canopy of beech trees, but there is sparse understory to help secure soil. Several recent freeze-thaw erosion events were documented this winter where freezing nights were followed by winter rainfall, leading to rapid movement of soil. Some erosion pins were completely buried in frozen sediment, so that they could not be measured until the next warm day. Data is still being collected, but these winter freeze-thaw measurements are already significant to the study!

Erosion is a complicated natural process, and scientists are still untangling the many mechanisms that may play a role in its impacts. However, there are some things that are very clear. Planting dense vegetation along stream banks combats severe and frequent freeze-thaw cycles. In addition, proper stormwater runoff management is vital for keeping soils stable as winter rainfalls increase in frequency. Freeze-thaw cycles themselves are normal for this area, but it is important to make sure that the rate of erosion doesn’t outpace what local streams can handle. Protecting the land around waterways is essential for healthy habitat and clean water!

References:

Inamdar, S., Johnson, E., Rowland, R., Warner, D., Walter, R., & Merritts, D. (2017). Freeze–thaw processes and intense rainfall: The one-two punch for high sediment and nutrient loads from mid-atlantic watersheds. Biogeochemistry, 141(3), 333–349. https://doi.org/10.1007/s10533-017-0417-7 

Luffman, I., & Nandi, A. (2019). Freeze-thaw induced gully erosion: A long-term high-resolution analysis. Agronomy, 9(9), 549. https://doi.org/10.3390/agronomy9090549 

Wynn, T. M., & Mostaghimi, S. (2006). Effects of riparian vegetation on stream bank subaerial processes in southwestern Virginia, USA. Earth Surface Processes and Landforms, 31(4), 399–413. https://doi.org/10.1002/esp.1252