Studying Quality of Life with Aquatic Macroinvertebrates 

There is more than one way to find out the quality of life in our local rivers and streams. For example, a scientist may choose to make observations about the environment surrounding the river, while others prefer to collect and analyze the fish community. Whichever method a scientist chooses to take on for their analysis, they must make time for work in the field and inside the lab.  

“My passion is out in the fields,” says Brenda Vong, a recently graduated Drexel student from the Department of Biodiversity, Earth and Environmental Science. She enjoys photographing observations and taking in the view of a stream while pondering how its course changes over time and who inhabits it. “It is where I learn best, digging around the dirt or wading in streams. It is about the importance of getting intimate with nature.” 

It was outside during her coursework where Vong learned more about the world of macroinvertebrates and the important role they play in our aquatic ecosystem. 

Close-up of an Asian Clam (Corbicula fluminea) in Montgomery County, PA. little_blumen/iNaturalist 

What is a macroinvertebrate and why should we study them? 

Macroinvertebrates are animals that are large (or, macro) enough to be seen with the naked eye and lack a backbone (invertebrate). This includes crustaceans, worms, snails, clams and many insects, such as the dragonfly, who often spend their immature stage at the bottom of a waterbody or on nearby rocks and debris.  

These macroinvertebrates break down this leaf litter, cycle nutrients and act as prey for other organisms — all of which contributes to the survival of the overall aquatic ecosystem. Macroinvertebrates are sorted into different feeding groups, including shredders, collectors, grazers, predators, parasites and filter feeders.  

Blue Dasher (Pachydiplax longipennis). little_blumen/iNaturalist 

“Generally we want to see more shredder and collector macroinvertebrates farther upstream,” Vong explains, “because they contribute to the growth, biomass and survival of the ecosystem.” For example, shredders, such as cranefly larvae, process coarse organic matter such as wood debris and leaves while collectors, like Hydropsychidae caddisfly — who form nets on the rocks in riffle areas that act like a fisherman’s net — help filter, collect and then eat the matter broken down by shredders.  

Macroinvertebrates can also be indicators of pollution. Since the days of the Academy’s pioneering scientist Ruth Patrick, there have been state-level surveys and conferences occurring every year across the nation to help us better understand their environmental role. The Academy’s Macroinveretbrate Section in the Patrick Center is a crucial part of this research, continuing more than fifty years of bioassessment, biomonitoring and inventorying of rivers, streams, ponds and lakes throughout the United States. 

the introduced Chinese Mystery Snail (Cipangopaludina chinensis). little_blumen/iNaturalist 

What makes up a healthy aquatic ecosystem? 

Some macroinvertebrates are very sensitive to pollution, while others,which can often be invasive species, tolerate higher levels. A healthy aquatic ecosystem will have more pollution-sensitive macroinvertebrates.  

In the case of Park Creek at Deep Meadow Park, where Vong was studying, there was a lack of historical scientific data compared to other near-city water bodies, like the Wissahickon Creek or the Schuylkill River. Vong predicted that the creek was healthy based on visual observations and the township’s effort to restore the creek.  

“But upon my analysis,” Vong explains, “I learned that some organic pollution is still probable at Park Creek.” She took a total approach, categorizing macroinvertebrates into their feeding group and their abundance and pollution tolerance values, as well as using some mathematic calculations, such as the Hilsenhoff Biotic Index. 

Macroinvertebrates do not respond to all pollutants and they are best studied alongside other factors like water chemistry, fish, plants and sediment. This totality can provide evidence of whether our local aquatic ecosystems are healthy or polluted.  

Close-up of a crayfish (Family Cambaridae) in Montgomery County, PA. little_blumen/iNaturalist 

Simple appearances can be deceiving and pristine-looking rivers may actually be polluted, as Vong hypothesized. So, she believes, communities should always respect the environment. 

“I think that collecting and identifying macroinvertebrates is an inclusive and hands-on project that many local communities can do to learn more about their water and how to protect them,” Vong says. 

Whether getting the community to work together to plant more native plants around the river, limiting the amount of pollution and run-off wasteflow or learning where our water comes from and its history, Vong believes we can make an environmental difference in any creek or river by joining together.  

“We don’t like sewage in our water, and neither do insects!” 

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