Downward oxygen trend a risk for salamanders

Barton Springs is the only known home to the endangered and federally protected Barton Springs and Austin Blind salamanders. Unfortunately, for these unique creatures, the level of life-sustaining dissolved oxygen in their ecosystem has dropped on average over the past 35 years.

Watershed Protection Department engineer Abel Porras brought the issue to the Wednesday meeting of the Environmental Board, noting that water flow in the Edwards Aquifer is a major determining factor in the equation, though man-made contaminants may also play a role.

“We need to maintain flow at Barton Springs in order to maintain dissolved oxygen,” Porras told the board. Ultimately, he added, more work, research and data are necessary to understand exactly how much dissolved oxygen the salamanders need to stay healthy and whether the downward trend in levels will continue.

Board Chair Mary Gay Maxwell called the findings “disturbing.”

Porras followed up with the Austin Monitor on Friday. “There’s still a lot of ambiguity on how much dissolved oxygen is healthy for the salamanders,” he said. “It ranges between 3 and 4 milligrams of dissolved oxygen (per liter). Right now, our median is around 5 or so, so we’re in a good range.”

Porras added that this does not mean the salamanders are unaffected by decreasing levels, however. “There has been an impact on the salamanders,” he said. “We just don’t know the extent of it.”

Porras said that many factors could influence flow in the Edwards Aquifer, but that pumping from it is certainly one of them. Pumping from the Trinity Aquifer may also affect flow in the Edwards, he added, though more research is necessary to know for sure.

The introduction of other nutrients like nitrogen and phosphorus to the aquifer through runoff and other means, Porras continued, could also affect dissolved oxygen levels. “What those tend to do is allow biological growth of other things, and those things, in order to live, consume a lot of the dissolved oxygen in the water,” he said.

On-site sewage facilities, such as the septic tanks that Porras said have “proliferated” in South Austin, could also contribute such nutrients to the aquifer.

Part of the solution, he explained, is to continue to work with the Barton Springs/Edwards Aquifer Conservation District, which can help maintain water flow in the aquifer.

“We’re working hard with the district, we’re collecting data and doing a lot of analyses, and they’ve been very helpful for us also,” Porras said. “I think it’s definitely a collaborative effort and one that’s needed, certainly.”

Photo by Wordandgesture (Own work) [CC BY-SA 3.0], via Wikimedia Commons