Gonzales springsnail Tryonia circumstriata
ESA status: candidate for listing
The thirst for water in the American West has taken a heavy toll on freshwater springs, which are critical habitat for fish, wildlife, and plants. Groundwater pumping and water withdrawal in West Texas have caused many springs to cease flowing or diminished flow to a trickle. Only one major spring is still flowing in Pecos County, Texas: the Diamond Y Spring, home to the tiny Gonzales springsnail.
The Diamond Y Spring is located on the 3,962-acre Diamond Y Spring Preserve owned by the Nature Conservancy, one of the largest and last remaining cienega systems in West Texas. The Gonzales springsnail lives in two separate stream segments—totaling about 1.5 miles—that flow from the spring. The Diamond Y Spring complex also supports two endangered fishes (Leon Springs pupfish (Cyprinodon bovinus) and Pecos gambusia (Gambusia nobilis)), a semi-aquatic endangered snail (Pecos assiminea (Assiminea pecos)), the threatened, salt-tolerant Pecos sunflower (Helianthus paradoxus), four other globally rare plants, and a suite of other rare aquatic invertebrates.
Texas state law and local rules generally do not support groundwater conservation to preserve spring flows. Springs within 8 miles of Diamond Y Spring, one of which had a much greater flow than the Diamond Y, went dry decades ago, eliminating habitat for rare fish and aquatic invertebrates. The flow at Diamond Y Spring is very low and effects from groundwater pumping could be substantial. Although the Diamond Y Spring is owned by the Nature Conservancy preserve, the organization has no control over groundwater pumping outside the preserve.
The Diamond Y Spring is also located in an active oil and gas extraction field. Active wells are located within 300 feet of surface water and a natural gas refinery is 100 feet upslope from the spring; old brine pits are just a few feet from the spring and oil and gas pipelines cross the spring outflow where the Gonzales springsnail occurs. Springsnails are highly sensitive to water pollution and any spills, leaks, or leachate from oil and gas wells, refineries, pipelines, or brine pits at Diamond Y Spring could be detrimental to the Gonzales springsnail.
As if groundwater pumping and oil and gas extraction were not enough, the Gonzales springsnail is also threatened by climate change and the exotic Melanoides snail, whose populations are so dense they virtually cover the underwater surfaces along parts of the spring outflow. Despite its location on a nature reserve, and its co-occurrence with other listed species, the Gonzales springsnail needs legal shields. The U.S. Fish and Wildlife Service designated the Gonzales springsnail as a candidate for protection under the Endangered Species Act in 1989 due to the continuing threats from groundwater pumping, oil and gas extraction, and invasive species this species faces.
Freshwater springs are vital to rare and endemic species. Springsnails are important indicators of water quality and quantity in springs. Protecting springsnails helps preserve spring environments, safeguarding treasure troves of western biodiversity.
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photo credit: Robert Hershler, Smithsonian Institution