Researcher looks into declining mussel populations in Texas rivers

two women in SCUBA gear hold mussel shells

Image: AgriLife Research

Jennifer Morton hovers methodically over a row of clear, water-filled containers on a tight-spaced industrial shelving system. She plucks a mollusk from one of the containers, observing the specimen as part of a study on freshwater mussel tolerances.

The activity is part of an ongoing effort at the Texas A&M AgriLife Research and Extension Center in Dallas to address declining freshwater mussel populations across the state – a trend that could signal declining health in Texas’ river systems, Morton said.

Morton is a research assistant with the Texas A&M Natural Resources Institute, a unit of Texas A&M AgriLife Research.

“Freshwater mussels provide a service to the ecosystem as filter feeders,” she said. “They help to clean the water, filter sediment, and contribute to nutrient cycling. They draw nutrients from the water and make them available to other organisms.”

Of the 52 freshwater mussel species in Texas, 15 are listed as threatened by extinction at the state level, according to the Texas Parks and Wildlife Department. Of those 15, 11 are candidates for “endangered” status under the U.S. Endangered Species Act.

“Mussels are indicators of healthy rivers,” Morton said. “They are resilient animals, so the disappearance of mussels from a river can be a sign of long term water pollution problems. By improving water quality for mussels, we would also improve quality for people who rely on these rivers for drinking water and recreation.”

Morton’s work studying trends that lead to widespread mussel decline is housed at AgriLife’s Dallas Center but implemented by the Texas A&M Natural Resources Institute. The institute aims to improve conservation and management of natural resources through interdisciplinary and applied research.

Morton recently entered the U.S. Fish and Wildlife Service’s 12-week Directorate Resource Fellowship Program at the organization’s San Marcos Aquatic Resources Center. There she will begin new research into declines of the Texas hornshell mussel, which in late 2016 became the first state species proposed for listing as nationally endangered. The official listing process, which includes a period for public comments, is ongoing.

Morton’s research with the fellowship program involves observing physiological tolerances and reactions of mussels to “dewatering” – an increasingly critical area in the face of climate change, drought and rising water demands, she said.

She said Texas hornshell populations are especially important to ecosystems along the Rio Grande, where “there is a pretty low diversity of mussels to begin with.”

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