By Watershed Protection Program Co-op Sally Ehlers

Have you ever heard of the New Zealand mudsnail (Potamopyrgus antipodarum)? These tiny creatures, each just a few millimeters long, are causing big problems in some Pennsylvania streams and rivers.

The New Zealand mudsnail is an invasive species, which means it is not native to the area where it is now living. This species is native to the freshwater streams and lakes of New Zealand and neighboring islands. They do not cause any trouble there because native parasites and predators keep their populations from growing too large. 

However, in the United States, this species has no natural parasites or predators, which allows populations to explode in waterways where they are introduced. This species was first discovered in the United States in the late 1980s, and it has since spread to many different parts of the country, arriving in Pennsylvania in 2006. In Pennsylvania, New Zealand mudsnails have been found in several rivers and tributaries, including the Schuylkill River, Wissahickon Creek, and Wyomissing Creek.

You can identify these snails by looking at their rice-sized shells. New Zealand mudsnails are right-handed which refers to their shell’s coiling direction. When viewed from the top, the shell of a right-handed snail coils clockwise. They also typically have five to eight whorls, or complete rotations of the spiral shell.

One of the reasons the New Zealand mudsnail is such a threat is that it reproduces asexually, so it only takes one snail to spread the population to a new waterway. A single snail can produce thousands of offspring in just one year. In some infested waters, these snails can reach densities of hundreds or even thousands of snails per square foot. That means they can quickly take over habitats and outcompete other species for food and space. One concern is that they could be displacing other snail species that are important food sources for fish and other animals. They also eat a lot of green algae which can result in altered nitrogen levels in the waterway. Changes can potentially hurt the ecosystem’s health because too little nitrogen can stunt plant growth while excess nitrogen can lead to eutrophication. 

These snails can attach themselves to boats, fishing gear, and other equipment. This means that people who fish or kayak in an area with New Zealand mudsnails could unknowingly transport them to other waterways, spreading the invasion even further.

So what can be done to stop the spread of these snails? One important step is to clean your gear thoroughly if you’ve been in contact with infested waterways. This means washing your boots, waders, and other gear. Techniques known to effectively disinfect gear from these mudsnails include putting your gear in the freezer for at least six hours or soaking it in really hot water (greater than 120 degrees Fahrenheit) for at least five minutes. Another way is to soak your gear in chemicals, either a 50/50 mixture of water and Formula 409® Cleaner Degreaser Disinfectant or 2% Virkon Aquatic, for 20 minutes. It is important to note that other cleaning agents, like bleach, are not as effective against New Zealand mudsnails.

The New Zealand mudsnail is a significant issue in some Pennsylvania waterways. By taking steps to prevent their spread, we can help protect our native ecosystems and the animals that depend on them. WCT’s Watershed Protection team has not found any New Zealand mudsnails in Ridley, Crum, or Darby Creek to date, but they continue to check and clean their equipment thoroughly whenever they are working in the field. 

If you find a New Zealand mudsnail, report it to Pennsylvania Fish and Boat Commission by calling 815-359-5163 or visiting their website. 

References:

“New Zealand Mud Snail,” Pennsylvania Fish and Boat Commission,

https://www.fishandboat.com/pages/New-Zealand-Mudsnail.aspx

“PFBC Urges Anglers and Boaters to Help Prevent Spread of Invasive New Zealand Mudsnails,” Pennsylvania Pressroom, https://www.media.pa.gov/pages/fish-and-boat-commission-details.aspx?newsid=445

“Potamopyrgus antipodarum,” U.S. Geological Survey, https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=1008

“Potamopyrgus antipodarum (New Zealand mudsnail),” CABI Compendium,

https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.43672#toimpactEnvironmental

By Watershed Protection Program Co-op Sarah Barker

Biofilms are all around us! Often thought of as pests in any environment humans find them, these overlooked communities are wonderous mini ecosystems that power some of our most treasured natural habitats. “Biofilm” is a catch-all term used to describe communities of primarily fungi, bacteria, micro and macro algae, viruses, and an ancient group of single-celled organisms called archaea that, together, can thrive in extreme environments, living in a kind of micro-city. Depending on where they are found, the numbers and types of different little creatures living within a given biofilm can change wildly. 

Most of the organisms that live in biofilms are very specific about what conditions they need to survive and thrive. Factors like temperature, light availability, and moisture or humidity can completely change what kinds of algae, fungi, bacteria, archaea, viruses, and other organisms decide to join that community.

Biofilms can be found in any number of places from desert sand to the backs of your teeth! However, your dentists don’t love biofilms, because they can accumulate cavity-causing bacteria if you don’t brush your teeth often enough. Biofilms can also be destructive to man-made objects and buildings. When it comes to water pipes, any submerged concrete, or regular stone buildings, biofilms can worsen natural weathering, create cracks, or even destroy the entire structure given enough time. 

However, biofilms are also, surprisingly enough, quite useful in some industrial, agricultural, and sanitary operations like breaking up toxins from chemical spills and promoting root growth in crops. They can also be used in facilities to treat wastewater for certain kinds of toxins. Studies show that freshwater biofilms serve as an essential “sink” for some toxic trace metals like arsenic. What this means is that they can take up these metals, store them, and over time, turn them into other molecules that can be used by the ecosystem safely!

The main difference between the two functional extremes of nuisance and foundation of the food web is the unique mixture of methods an individual biofilm will use to produce and use energy.

There are two main ways that biofilms can generate or consume energy: through oxygen-driven processes like photosynthesis, or chemical reactions which happen in areas lacking oxygen. These chemical reactions, mostly caused by bacteria or archaea, are essential sources of nutrients including nitrogen for freshwater ecosystems. 

Almost every biofilm will have a combination of these processes happening at the same time. Bacteria and archaea will generate chemical reactions that produce molecules needed by another member of the biofilm like diatoms (microscopic single-celled algae) in order to start photosynthesis. Therefore, each individual part of the biofilm contributes to a vast network of chemical reactions and energy exchanges that can enrich or maintain an entire ecosystem.

Biofilms can play any number of roles in a habitat. In desert ecosystems, biofilms act as anchors, using their sticky materials to bind sand grains together, which allows plants to start growing without being ripped from their positions by the strong winds. In rivers and streams, biofilms are major producers of energy for the whole food chain, and out in the ocean, biofilms are responsible for taking a great deal of nutrients and oxygen from the air and making them available in the water for other creatures to use. 

However, maybe most impressively, biofilms are the main producers of energy for areas that feature many ice sheets, like polar ice valleys and ice-covered lakes. Biofilms truly are fascinating forces of nature capable of sustaining an entire ecosystem, destroying structures, cleaning our water, fertilizing crops, and even causing cavities. So the next time you see a slimy film on a rock, thank your little biofilm friends for all their hard work!

References:

Barral-Fraga, L., Martiñá-Prieto, D., Barral, M. T., Morin, S., & Guasch, H. (2018). Mutual interaction between arsenic and biofilm in a mining impacted river. Science of The Total Environment, 636, 985–998. https://doi.org/10.1016/j.scitotenv.2018.04.287 

Bharti, A., Velmourougane, K., & Prasanna, R. (2017). Phototrophic biofilms: Diversity, ecology and applications. Journal of Applied Phycology, 29(6), 2729–2744. https://doi.org/10.1007/s10811-017-1172-9 

Romani, R. M., Guasch, H., Balaguer, M. D., & de Montilivi, C. (2016). Aquatic biofilms: Ecology, water quality and wastewater treatment (1st ed.). Caister Academic Press. 

Zijnge, V., van Leeuwen, M. B., Degener, J. E., Abbas, F., Thurnheer, T., Gmür, R., & M. Harmsen, H. J. (2010). Oral biofilm architecture on natural teeth. PLoS ONE, 5(2). https://doi.org/10.1371/journal.pone.0009321 

By Watershed Conservation Research and Data Specialist Anna Willig

Aquatic macroinvertebrates — animals without a backbone that are visible to the naked eye — are some of the most fascinating creatures found in streams. We tend to lump all macroinvertebrates into one category, but there is tremendous diversity found underwater. 

Some macroinvertebrates live for a few weeks, others for a few years. Some stay burrowed in the streambed their entire lives, others emerge as flying adults and migrate across the country. Some scrape algae off of rocks, others are voracious hunters. To illustrate this diversity, we are highlighting three sample orders from the class Insecta (the insects) that have vastly different life histories. While there are generalities that are shared between all species of each order, this is akin to generalizing the life history of all passerine birds (order Passeriformes, which includes most songbirds). 

Odonata Spotlight | The Dragonflies

First up is the order Odonata, which includes dragonflies and damselflies. Dragonflies and damselflies are similar, but we focus on dragonflies, which are unique among aquatic macroinvertebrates for their large size, long lifespan, and hunting prowess. Dragonflies start their lives as eggs laid near the surface of the water. Eggs hatch within a few weeks, but some dragonflies can delay hatching for a year if they sense stream conditions are suboptimal. Once they hatch, they typically spend less than a year underwater in the larval (juvenile) stage, though some species spend up to six years developing in streams. Larval dragonflies are fearsome hunters that eat anything they can catch, including other insects, small fish, and tadpoles. 

In their final days as larvae, dragonflies stop eating! During their metamorphosis from larvae to adult, their mouthparts change and, for a few days, are not functional. They crawl onto land at the end of their metamorphosis and climb out of their larval skin, emerging as adults. Once their wings dry and harden, adults take to the air, where they are as ferocious as they are underwater. They have remarkable vision and can predict where their prey will go, a feat not seen in other insects. Males establish territories over water, keeping other males out and luring females in. 

Adult dragonflies live for several months to a year, and a few species, including the Common Green Darner (Anax junius), migrate across the country. Much remains unknown about the migration of Common Green Darners, but, like Monarch Butterflies, a migratory cycle likely lasts a few generations. The first generation emerges in the late winter in southern states and flies north to mate and lay eggs. The second generation hatches in late spring and migrates in late summer, making their way south to a place they have never been. They mate and lay eggs in the south, and the final generation emerges in the fall. This generation overwinters in the south, mating and laying eggs for the next migratory generation.

Ephemeroptera Spotlight | The Mayflies

Our next order is Ephemeroptera, the mayflies. Like dragonflies, mayflies have an aquatic larval stage and a terrestrial adult stage, but they share few other similarities. Mayflies are the only insect with an extra phase of metamorphosis called the subimago life stage. They are short-lived as adults and, in ideal conditions, can form massive swarms. Mayfly eggs often hatch within a few weeks, though some species hatch immediately and others delay hatching for a year in suboptimal stream conditions. Mayflies spend up to two years as aquatic larvae, shedding their skin dozens of times before adulthood. While most larval mayflies eat algae, leaves, and other plant matter, a few are predators (though not nearly as efficient as dragonflies).

At the end of their larval stage, mayflies crawl out the stream and shed their larval skin. However, they are not yet adults. This post-emergent, pre-adult form is a life stage unique to mayflies called a subimago. Subimagos have a hairy covering over their wings and must molt one more time to remove this covering, after which point they are adults. Adults only live for a few hours to days. During this ephemeral time, they have one task: reproduce. They lose the ability to eat during their metamorphosis into adults, forcing them to focus all their energy on finding a mate instead of finding food. Males form massive swarms, sometimes large enough to be detectable by weather radar, twirling and dancing to attract females. Females fly into the swarm, find a mate, and speed off to the nearest body of water, where their final act is laying eggs. 

Coleoptera Spotlight | The Water Beetles

Another unique order is Coleoptera, the beetles, which is the largest order in the animal kingdom, containing an estimated 25% of all animal species. Unlike Odonata and Ephemeroptera, which include exclusively insects with an aquatic life stage, only a small fraction of Coleopterans have an aquatic life stage. Common water beetles include water pennies, diving beetles, and riffle beetles. Water beetles are aquatic for their larval and adult stages, only emerging for a few weeks to pupate. They hatch from eggs laid in the water, typically within two weeks, as most cannot delay hatching. Larval water beetles have diverse diets; some scrape algae off of rocks, some shred leaves, and some are predatory. They spend anywhere from a few months to a year in their larval stage and crawl onto the banks to metamorphose.

On the banks, larvae burrow into soft sand and mud to metamorphose, emerging as adults several weeks later. They fly briefly until they find a suitable place to enter the water. Once they re-enter the water, many water beetles never return to the surface. Some even lose their wings. Adults do not have gills and carry an air bubble to breathe, maintaining an equilibrium with the oxygen in the water that constantly replenishes their air. Some adults are short-lived and may not have mouthparts, while others can live for up to three years and have a variety of feeding strategies. Adults mate and lay their eggs underwater, setting the stage for the next generation.

Each of these orders contains multiple families, each family contains multiple genera, and each genus contains multiple species, each with a unique life history. Each stream contains its own community of macroinvertebrates, an unknown diversity hiding just beneath the waters.  And these insects are not exclusive to local streams —  there are thousands of species of dragonflies, mayflies, and water beetles found on all continents except Antarctica. Since 2018, the Watershed Team has collected annual macroinvertebrate samples from the headwaters of Ridley, Crum, and Darby Creeks. We are busy sorting and identifying our samples and are looking forward to sharing what these unique creatures can tell us about local stream health.

References and Resources

Voshell, J. R. (2002). A guide to common freshwater invertebrates of North America. McDonald & Woodward Pub.

Interested in learning more about macroinvertebrates? Check out macroinvertebrates.org for information about and pictures of many of our local macroinvertebrates.  

By Watershed Conservation Research and Data Specialist Anna Willig

One of the most basic, yet most critical, aspects of stream health is temperature. Temperature sits behind the scenes, governing nearly everything that happens in a stream. Make a stream too warm or too cold, and the wildlife will disappear. 

While measuring the temperature of a stream seems straightforward — just stick a thermometer in the water — the reality is much more complicated. In small streams, such as the headwaters of Ridley, Crum, and Darby Creeks, temperature is incredibly variable. At the same spot in a stream, temperature can change by several degrees depending on the time of day, current weather, and time of year. Each day, water temperature rises and falls with the sun. Weather matters — a hot, sunny day will warm a stream more than a cool, cloudy day. Temperature also changes with the seasons, rising throughout the spring and summer and dropping in the fall and winter. 

Location in a stream is important as well. In shady areas, streams will be cooler than in sunny areas. Slow-moving stretches tend to be warmer than fast-moving areas. Muddy water gets warmer than clear water. Shallow areas can warm more than deep sections. The variation of water temperature over time and across space in streams makes it crucial to measure temperature many times at many places in a stream in order to understand temperature trends.

Changes in land use further alter water temperature. When forests are leveled and replaced with strip malls and subdivisions, streams heat up. In undeveloped areas, rainfall soaks into the ground and cools as it flows underground towards streams. In developed areas, rainfall instead runs off of (often hot) parking lots, roads, houses, and sidewalks right into streams. This water cannot cool off and can make streams hotter. Removing streamside trees, building dams, and creating ponds all expose water to more sunlight, ultimately heating the stream.

Add in climate change, which will warm our region drastically in the next few decades, and it is clear that our streams are heating up. But why is this a problem? What does temperature have to do with the animals that live in our streams?

The danger of warm water temperature starts at the molecular level. Temperature governs the rate of chemical reactions and, in water, the amount of oxygen available. As a stream warms, chemical reactions occur faster and the water holds less oxygen. Most animals that live in streams — insects, mussels, fish, frogs, turtles — are cold-blooded, meaning their body temperatures change with the stream temperature. If a stream warms up, so will body temperature, speeding up respiration, metabolic reactions, and all other internal chemical processes that keep the animal alive. However, since warm water holds less oxygen, there will be less oxygen to support these processes, causing stress. 

This thermal stress affects how fast organisms grow, how big they get, and how well they reproduce. Researchers from Stroud Water Research Center tested the impacts of water temperature on aquatic insects, which form the base of the food chain in streams. While there was a threshold above which all insects died, there were concerning effects even before temperature reached lethal levels. As temperatures warmed, insects developed and matured faster, but they did not become as large and consequently struggled to reproduce. If streams become too hot for aquatic insects to survive and reproduce, they will disappear, with catastrophic consequences for the entire ecosystem. 

Fish are also sensitive to changes in stream temperature. Brook trout, Pennsylvania’s only native trout, currently cannot reproduce in local streams because temperatures are too warm. Even though trout are stocked by anglers every spring in local streams, the thermal stress forces these fish to devote so much energy to survival that they have no energy left for reproduction. Even less sensitive types of fish, like bass and sunfish, will show signs of stress when temperatures get too high.

If we want to keep our streams healthy, if we want to protect all the animals that depend upon them, we need to keep them cool. Limiting deforestation, especially along stream banks, will protect shady areas that cool streams. Establishing and expanding forested streamside buffers will create new shade and cool streams. Limiting new development will prevent the expansion of hot pavement. Shifting from stormwater management strategies that hold water, such as retention basins, to strategies that encourage infiltration, such as rain gardens, will force more water into the soil, where it can cool before reaching a stream.

You can make a difference at home by replacing lawns with gardens or meadows full of native plants, which will allow more water to enter the soil. Adding rain barrels will reduce the amount of hot runoff flowing off rooftops into streams. Planting trees, even if you are far from a stream, will also cool water down. Climate change means that rising temperatures will remain a constant threat, but making stream-conscious decisions can help ensure our streams remain healthy and full of life. 

References and Resources

Check out this lecture on temperature from Dr. John Jackson of Stroud Water Research Center (lecture starts at 18:20): https://youtu.be/8Y1ey45053Q?t=1100.

Check out this research article about the impacts of temperature on mayflies from Stroud Water Research Center.

To see a streamside buffer restoration in progress, visit the Watershed Team’s Tree Planting at Ashbridge Preserve! Since 2019, we have put in nearly 1,500 trees with the goal of lowering water temperature in Ridley Creek.

By Watershed Protection Program Director Lauren McGrath

Welcome to Willistown Conservation Trust’s 2023 Creek Week! We are so excited to have you join us on a meandering exploration of stream ecosystems — from the tiniest single-celled member of the biofilm to one of the largest rodents on the planet — there is so much to learn about in the Watershed Program’s favorite ecosystem. 

This year, we begin with one of the most critical pieces of determining a stream’s health and function: water temperature. Water temperature dictates the ability of stream life to survive and thrive, and as stream temperatures increase, so does the stress level of sensitive species, like brook trout and macroinvertebrates; a perfect segue to day two of Creek Week, where we will be learning more about the life cycles of different stream insects! Dragonflies, mayflies, and riffle beetles all play an important role in ecosystem health in all of their life stages.  

On day three, we look at what powers the insect base of the food chain: Biofilms! These microscopic ecosystems are all around us and play important roles in transforming light and chemicals into energy, often without much celebration. Learn more about how biofilms are present all around the world — even within your own body.

While we love to celebrate the diversity of endemic, or native, macroinvertebrates, we would be remiss if we did not dedicate a day to learn about one of the newest arrivals to local streams: the New Zealand mudsnail. Join us on day four to take a deep dive into a potentially disruptive new arrival, which has been documented around southeastern Pennsylvania in the last several years. These little snails can form populations so dense that they remove the biofilm from a stream completely! 

While invasive species can be very small like the New Zealand mudsnail, invasive species can also be quite large. Day five brings us face to face with the infamous Northern snakehead, an Asian fish that was first discovered in 2004. Learn more about this frightful predator’s unique adaptations that make it difficult to fully remove from a waterway. 

Finally, we end with the colorful Tale of Charlie Woodscomb: a True Beaver Pioneer. Learn more about the behaviors of beaver through the eyes of Charlie, known fondly as Chompy, as he explores his environment looking for a healthy ecosystem to build a life.

We hope to see you out in the stream, and we invite you to join us for our Watershed Volunteer Day on June 24 and our Streams Learning Evening on June 26!