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What's in a Healthy River Ecosystem?

The Wissahickon Creek, Image by Kiara Buker

What factors determine the health of a river or creek? Do you know if your home has a healthy river ecosystem? There are more to look at than sight alone to conclude if a water source is healthy for sustaining life. Like all other ecosystems you can imagine, a river ecosystem is made up of biotic and abiotic components. Biotic, or “life” includes all living organisms such as plants, animals, bacteria, fungi, etc., whereas abiotic, “without life”, are the non-living chemical and physical structure which living organisms can interact with or are affected by. An ecosystem cannot thrive without one or the other because “...organisms respond to their physical environment…” (D'Angelo, Gregory, Ashkenas and Meyer 1997, p. 481)

Starting with what is most visible to our eyes, biotic factors. What do you see around the there an abundance of plants? Plants could tell us if the river ecosystem is healthy or unhealthy, for example, the site is overtaken by invasive species and is overgrown! Not only would there be a lack of native plants and biodiversity, it would weaken the bank’s stability, degrade the water quality, and it’s visually unappealing! Tree canopies-- how much shade are they providing for the river? Are they stabilizing the streambank and reducing erosion? The same applies to fish and other aquatic organisms that live in the river ecosystem.

“Is there an invasive species? How many species of fish are there, how much of each is there, and how big or small are they? Are there plenty of macroinvertebrates throughout all velocities of water?” And who knows, it can be a fun learning experience to find out how many macroinvertebrates live in rivers because they are so small, they can practically be invisible!

A tree in the Wissahickon providing shade, Image by Kiara Buker

With abiotic factors, checking the water chemistry such as the water temperature and dissolved oxygen (DO2) is a great way to determine the health of a river. A higher temperature and lower DO2 makes a difficult environment to sustain a diversity of fish and aquatic organisms. The pH and salinity (measure of dissolved salts) can also tell you if water is inhabitable for organisms. Specific conductivity (the measure of water’s capability to pass electrical flow) tells us if there are nutrients present like phosphate, nitrate and sodium, which can be used by algae. Something more visible to our eyes is sediment or “substrate” (cobble, granule, sand, pebble, etc.).

“Is there too much of one substrate? Or is there too little of one substrate for organisms to stay in a certain water flow? How much algae is visible on the substrates? Do these substrates stunt an organism’s ability to lay eggs or hide?” These are the sorts of questions you might ask yourself when you are working with sediment.

Distributions of Earth’s water, Image by Dr. Timothy Bralower, Pennsylvania State University

After learning about what factors make up a healthy river ecosystem, some of you may be wondering, “Why do we need to know this information?” There is only 3% of freshwater on earth, many of which are trapped within glaciers, polar ice caps, atmosphere, and soil, or are too polluted or far below earth’s surface. Having access to clean water is considered and argued by many as a human right. So it is also our responsibility to keep our rivers, creeks, watersheds and all other bodies of water well-maintained; and knowing how we interact with the environment around us is a key part in protecting our water. It can be as simple as keeping litter out of the water, volunteering at your local watershed, or empowering the next generation of environmental scientists and stewards like our Watershed Stewardship Program, ProFESS.

We rely on water in our daily lives, whether the purpose is to use it for agriculture, drinking, fishing, cleaning... water is important. And no matter where you are, there will be communities protecting their watersheds, and with enough work and time, a river can be healthy once more.


D'Angelo, Donna J., et al. “Physical and Biological Linkages within a Stream Geomorphic Hierarchy: A Modeling Approach.” Journal of the North American Benthological Society, vol. 16, no. 3, 1997, pp. 480–502. JSTOR,

Fondriest Environmental, Inc. “Conductivity, Salinity and Total Dissolved Solids.” Fundamentals of Environmental Measurements. 3 Mar 2014. Web. < >.


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