As tropical fish move north, UT San Antonio researcher tracks climate threats to Texas waterways

University of Texas at San Antonio

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Assistant Professor Matthew Troia will use the NSF CAREER award to investigate how climate change and urbanization are affecting freshwater ecosystems by enabling exotic tropical fish species to expand northward.

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Credit: The University of Texas at San Antonio

The National Science Foundation has awarded a UT San Antonio assistant professor of biology, health and the environment the distinguished Faculty Early Career Development Program (CAREER) award.

The assistant professor, Matthew Troia, will use the award to investigate how climate change and urbanization are affecting freshwater ecosystems by enabling exotic tropical fish species to expand northward.

“We hope our research will provide a deeper understanding of how biodiversity responds to increasing human impacts on the environment,” Troia said. “Our goal is to create practical tools and strategies that natural resources managers can use to protect Texas waterways.”

Read more about the project on the NSF website.

During the next five years, his project will integrate lab experiments, extensive field monitoring, and computer modeling to better understand the vulnerability of Texas waterways.

“This study will provide new tools for natural resource practitioners to manage and mitigate the impacts of exotic species, climate change, and urbanization on freshwater ecosystems,” Troia said. “Maintaining healthy freshwater ecosystems is essential for human societies, particularly in arid regions like central Texas, where freshwater is inherently scarce.”

Lab experiments and field studies

Since 2019, Troia’s team has been monitoring the temperature of rivers and springs throughout Central Texas. The data, combined with lab-based measurements of fish physiology, offers unique insights into how aquatic species respond to temperature changes.

The NSF CAREER award will allow Troia to expand this work into performing laboratory experiments measuring cold tolerance, behavioral responses and metabolic changes in tropical fish species. It will also fund his work to conduct field studies that track temperature dynamics across urban and relatively more pristine waterways in San Antonio and its surrounding areas.

Troia’s team will study three tropical fish species already present in San Antonio waterways: the suckermouth armored catfish (pleco), Rio Grande cichlid and Mexican tetra.

These species have not yet established populations in North Texas, making them ideal candidates for exploring how warming temperatures and urban heat islands may drive future northward expansion.

Though freshwater systems cover less than 1% of Earth’s surface, these environments disproportionately support nearly 6% of all identified species.

“Studying these systems provides one of the highest returns on investment for conservation research,” Troia said.

The project will investigate how far north the species could spread under current climate trends by examining how warmer urban environments alter stream temperatures, how low temperatures affect tropical fish survival and growth, and whether riparian restoration strategies can mitigate heat effects.

Course credit and skills for students

The project also emphasizes research training for UT-San Antonio students. Troia will partner with Mariah Hopkins, professor of instruction and an expert in Course-based Undergraduate Research Experiences (CUREs), to embed several of their research objectives into classrooms.

CUREs are course-based undergraduate research experiences that allow students to conduct research for course credit and gain hands-on scientific skills.

Undergraduate students will participate in lab experiments, modeling exercises and data analysis that directly support the grant’s goals. The award also provides funding for students to attend scientific conferences where they will present their research and build their professional networks.

By 2030, Troia’s team hopes to produce interactive online maps that municipalities and agencies such as Texas Parks and Wildlife and the San Antonio River Authority can use to guide management decisions and restoration efforts.