Tuesday, February 17, 2026
UNT NSF grant study examines warming effects on freshwater stream ecosystems
DENTON (UNT), Texas 鈥� Research taking place at the aims to challenge conventional thinking in the world of ecology. Typically, research shows that organisms in warmer temperature waters mature faster and reach smaller adult sizes than those in cooler temperatures.
鈥淲hat we鈥檝e been seeing in the wild is the opposite,鈥� said Jim Junker, a research assistant professor in the . 鈥淭here鈥檚 a lot more bigger organisms than we expected compared to the amount of smaller organisms. Our goal is to get in there and disentangle the mechanisms behind this.鈥�
UNT College of Science's Jim Junker
Junker is one of the principal investigators on the project alongside two colleagues, Jeff Wesner from University of South Dakota and Justin Pomeranz from the Colorado Mesa University. This latest grant from the National Science Foundation is the next step in their effort to understand how temperature, energy availability, and body size combine to shape freshwater food webs.
鈥淏ody size distribution is a dominant driver for lots of biological and ecological functions. It shows us how energy moves through an ecosystem from algae up to larger predators,鈥� Junker said.
Traditional lab experiments suggest that warming temperatures lead to smaller body sizes and less energy reaching top predators.
鈥淗owever, a lot of those experiments are built on thinking of systems as closed,鈥� Junker said. 鈥淲ell, natural streams are open and collect all kinds of things from the landscape like fallen leaves or acorns.鈥�
To test these ideas in real-world systems, Junker and his team will visit streams maintained by the National Ecological Observatory Network, a program sponsored by the National Science Foundation. They鈥檒l be going to 24 different sites across the U.S., including Puerto Rico and Alaska. This will allow them to study ecosystems at various temperatures, latitudes and longitudes, and with varying sunlight availability.
鈥淭here鈥檚 some hope that we鈥檒l discover patterns that can let us make predictions as to how these systems may change in the future. For instance, as northern latitudes warm, they may change to reflect current ecosystems at lower latitudes.鈥�
For field research, the team鈥檚 most important tool is a ruler. They鈥檒l be measuring the size of insects and fish in the streams. They鈥檒l also catch some and place them in containers to measure the change in oxygen over time to calculate the metabolic rate of each creature as a proxy for its energy use. Junker sees this work as a good opportunity for students to get hands-on experience.
鈥淲e have two sites within an hour鈥檚 drive of UNT, so I鈥檓 hoping to involve a lot of undergrad researchers at UNT to help,鈥� Junker said. 鈥淚deally, they鈥檒l be able to create their own projects from this to help answer smaller questions that come from the work.鈥�
The grant, around $550,000, lasts for three years. The plan is to perform trial data collection in the spring with a full campaign planned for 2027. The teams will split into three groups and split up the U.S. with meet ups at the start and end.
鈥淲e鈥檙e very excited about this project,鈥� Junker said. 鈥淚t鈥檚 a meeting between science鈥檚 control and nature鈥檚 chaos and realism to lead us to a better understanding of what we know of the world at large.鈥�
From 鈥� Research