Austin's two-year drought has introduced a new threat to the already endangered Barton Springs salamander: low oxygen levels in the water. Recent rains have improved the situation slightly, but there's still not enough dissolved oxygen to support a healthy population of the 3-inch amphibians, which breathe through gills.
Placed on the Endangered Species list in 1997, the salamander (Eurycea sosorum) lives only in the springs in and around Barton Springs pool.
According to Laurie Dries, a biologist with the city of Austin, reduced water flow leads to lower dissolved oxygen levels. "This causes a direct and indirect stress on the animals," she said. The recent dissolved oxygen concentration in the water was around 4 mg per liter; levels below that will cause some animals to die. Normal levels are between 5 and 6 mg per liter.
"This means there is less food, and the lower the oxygen level, the lower the energy that is available for the salamanders to turn into metabolic energy... When you have conditions where dissolved oxygen is low they are more likely to put it into just surviving and not reproduce; it would stress them that much more to try to reproduce. So if they can delay reproducing and just survive until then, then when conditions get better, they can put more energy into reproduction."
Pumps near two of the smaller springs help to re-circulate water, which creates turbulence and adds oxygen to the water. While the pumps give the surviving salamanders a fighting chance, the only long-term solution is a lot more rain.
David Johns, with the city's Watershed Protection Department said, "Rain will help the aquifer some, but it is really needed in the west to get Barton Creek flowing."
Bill Bunch, executive director of Save Our Springs Alliance, added, "The creeks which feed the springs aren't really flowing." The spring flows have dropped as low as 10 cubic feet per second (cfs) recently, and the record low from the 1950s was 9.6 cfs. The recent rains temporarily brought it up to 48 cfs, but then it quickly dropped back down to about 25 cfs. "There's some hope that we're entering a wetter cycle, but we're certainly not there yet," he said.
The salamander also faces threats from development in the area. According to Bill Seawell, Austin field supervisor for the U.S. Fish and Wildlife Service, "Pollution - including nutrients, toxics, and sediments - are also concerns as parts of the watershed are developed." Construction over the watershed contributes to sediment accumulating in the springs, which obstructs the salamander's gills and can also harm their eggs.
The city currently has 400 salamanders in its captive breeding program, according to Dries. "While it's great that we have this cushion, it isn't a real replacement for maintaining the wild population...It is notoriously difficult to re-introduce a species into the wild."
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