UTSA students take water sampling from the Cibolo Creek in an effort to identify levels of estrogen which could be harmful to aquatic life.
UTSA students take water sampling from the Cibolo Creek in an effort to identify levels of estrogen, which could be harmful to aquatic life. Credit: Scott Ball / San Antonio Report

One of Boerne’s hidden treasures might be off-limits to the public, but for scientists, it’s a place to gain field experience and a deeper understanding of the natural world.

This week, the University of Texas at San Antonio announced it had renewed its research partnership with Cibolo Preserve, a 644-acre island in an ever-growing sea of development established by San Antonio entrepreneur and philanthropist Bill Lende.

The preserve offers an example of what much of the fast-growing area on San Antonio’s northern exurban fringes would have been like before being converted to housing developments, malls, and office complexes. That makes it the perfect place for scientists to study how these changes are affecting the drinking water sources and wildlife habitat.

“It’s like a natural outdoor laboratory,” said UTSA assistant professor Brian Laub, who has been studying water quality in urban creeks for signs of urban runoff. Water from Cibolo Creek infiltrates the Edwards Aquifer, the main drinking water source for the San Antonio region.

“With the potential increase in development, we can start to understand the system now and look at how it changes over time,” Laub said.

Supporting this science was an important goal for Lende, an inventor who manufactured after-market air conditioning units for the Volkswagen Beetle in the 1970s. He and his brother went on to establish the Lende Foundation and supported a variety of causes, including UTSA research.

Within sight of neighboring housing developments, the ranch Lende bought in 1981 now hosts prairies where native grasses wave in the breeze. A high-quality stretch of Cibolo Creek flows through the preserve, surrounded by fern-draped cliffs and towering cypresses. High fences surround the preserve to deter would-be trespassers.

Before his death in 2016, Lende set aside the former ranch as a nature sanctuary and place for collaborative research. Since 2009, the university’s internal seed grant program has awarded approximately $66,000 for research at the preserve, UTSA public affairs specialist Milady Nazir said.

Besides UTSA, other researchers include scientists with state agencies like the Texas Commission on Environmental Quality and Texas Parks and Wildlife, as well as the neighboring Cibolo Nature Center and Farm. Areas of research at the preserve have ranged from bat echolocation to fish habitat.

This summer, Laub and his students have been sampling Cibolo Creek for estrogen, the female sex hormone.

Laub and his colleagues wanted to measure levels of estrogen in the creek and identify if it’s coming from sewage plant effluent, urban runoff, or natural sources. In high enough concentrations, estrogen can have a harmful effect on fish.

Twice a month since May, they’ve been collecting water samples from four separate points. They found low concentrations of estrogen upstream and downstream of a sewage plant discharge point.

The Cibolo Creek Credit: Scott Ball / San Antonio Report

That indicates it’s either coming from runoff or a natural source in the ecosystem, Laub said.

Yongli Gao, acting director of UTSA’s Center for Water Research, also has been taking water samples from the creek because the creek serves as a perfect example of a karst environment, where limestone fractures, sinkholes, caves, and springs allow water to flow readily between the surface and underground.

“The creek is very complex,” Gao said. “For some segments, water flow increases, and then some decrease. For some parts, they almost disappear” as water flows underground, he said.

UTSA graduate student Adeyeye Adebayo measures the water at different points along Cibolo Creek.
UTSA graduate student Adeyeye Adebayo measures the water at different points along Cibolo Creek. Credit: Scott Ball / San Antonio Report

Citizen scientists with Cibolo Nature Center also have been tracking herons raising their young at a rookery at the site, and conducting regular surveys for prairie birds and waterfowl, said Donna Taylor, an environmental scientist who serves on the preserve’s board of trustees.

Taylor, one of those who Lende entrusted with caring for the preserve, said these kinds of studies can help state agencies and academic scientists better understand the sensitive Hill Country environment in an era of rapid population growth.

“This part of Texas is very unique in the grand scheme of things,” she said. “We have very unique situations that really we don’t have a good understanding of. Our population is growing really quick, and so we really need to understand them better to protect them better.”

Brendan Gibbons

Brendan Gibbons is the San Antonio Report's environment and energy reporter.