Waller Creek is home to hundreds of species of plants and animals, large and small, which make up its ecosystem. The smallest of these animals are called macroinvertebrates. These tiny monsters are animals without backbones that can be seen with the naked eye. These little creatures play an essential role in Waller Creek’s ecosystem and are useful bioindicators to environmental scientists. Bioindicators are living organisms that indicate an environment’s overall health.
Environmental stressors, like pollution, can affect macroinvertebrates morphologically, viably, behaviorally, or physiologically. Because these animals are always present, easy to collect, have long lives, and have different pollution tolerances, they are essential to the study of Waller Creek’s ecosystem health. Each macroinvertebrate has a Hilsenhoff Biotic Index (HBI), which estimates its pollutant tolerance in its environment. A high HBI indicates a high tolerance and a low HBI indicates a more sensitive tolerance to pollution. Things like predators, low oxygen levels, high pH, and nitrate can be harmful to macroinvertebrates.
The Black Caddisfly
The Black Caddisfly lives in and around Waller Creek and is a useful bioindicator in streams. They are large and have a high sensitivity to pollutants in the water. While the adults fly around near streams, their larvae live in the water full-time. They rely on the oxygen in the water to survive, so pollution prevents larvae from surviving into adulthood.
These little flies are essential to Waller Creek! Their larvae are known as “shredders” because they break down organic matter. This process allows energy to be cycled back into the ecosystem.
The Kiowa Dancer
The Kiowa Dancer is a native damselfly that lives in the areas surrounding Waller Creek. This tiny monster feeds on other insects as it flies around the stream, and has a moderate tolerance to pollution.
The Zebra Mussel
The Zebra Mussel is a freshwater mussel that is invasive to Texas. They are named for their distinct striped shell pattern. These tiny monsters attach themselves to hard surfaces, and as an invasive species with no natural predator, their spread has become difficult to control. They can clog pipes, consume plankton, and render beaches unusable.
Urban Ecosystems Research Stream
The Freshman Research Initiative (FRI)
In this multidisciplinary research stream, students use techniques from chemistry, biology, molecular biology, microbiology, ecology, environmental science, geological science, and social science to study urban ecosystems.
The FRI currently focuses on studying the Waller Creek watershed that spans most of UT campus. With more than 50% impervious cover, it is the most densely developed urban watershed in Austin. This watershed provides an ideal testing ground to study urban ecosystem function and its response to restoration.
Team Stuart: Measuring the Quality of the Waller Creek Ecosystem, led by Dr. Stuart Reichler
Team Stuart focuses on testing Waller Creek for its E. Coli levels. They also perform microorganism and tree circumference sampling to determine the overall health of the creek’s environment.
Further research will specialize in determining the origin of the E. Coli, as well as how other factors, such as algae, affect the overall Waller Creek environment. This research is essential in determining the safety of Waller Creek’s urbanized environment. Improving our understanding will allow the city to perform more efficient restoration efforts.
Team Energy: Ecosystem Functions of Waller Creek, led by Dr. Mary Poteet
Team energy studies how the production of energy and nutrients in creeks is affected by urbanization. The team has a suite of environmental sensors along Waller Creek that measures energy production. Using that data, they can evaluate how algae growth, nutrients, and organic matter from land affect these rates of production. They use a variety of field and lab techniques including in-creek experiments, fluorescent spectrometry, and advanced chemistry.
Their goal is to quantify which urban stressors are responsible for altering energy production in creek ecosystems. One remarkable aspect of this is that energy production in creeks is directly tied to carbon dioxide production. This research can help measure how urbanization affects the production of this greenhouse gas near creeks and rivers.
Team Ruth: Identifying Various Pollutants Found in Waller Creek, led by Dr. Mary Poteet
Team Ruth has a variety of projects that use analytical chemistry techniques to concentrate Waller Creek samples before extracting, identifying, and quantifying the pollutants found in the creek. So far, these chemicals include heavy metals, polycyclic aromatic hydrocarbons, antibiotics, and pesticides.
Further research will focus on determining the sources from which these chemicals originate. This research is essential in reducing the number of pollutants in Waller Creek, thus allowing the city to restore ecosystem health to this urbanized environment.
Contaminants in Waller Creek
When Austin was named the capital of Texas in 1839, plans for building the city did not take Waller Creek into account. The creek cuts through several parcels on the gridiron layout that was designed, and as a result, it has suffered from poor water quality, erosion, and flooding problems.
Anthropogenic pollutants are contaminants that come from human activity. Among these are agricultural fertilizers, which access the creek via stormwater, cleaning products, which access the creek via sewage leaks, and antibiotics, which contribute to bacterial antibiotic resistance. These pollutants, among others, seep into our groundwater and make their way into our water sources. The diagram above demonstrates this process.