The U.S. Fish and Wildlife Service declared six species of freshwater mussels found in Central Texas as endangered and another as threatened on Monday.

Environmental scientists refer to freshwater mussels as “the liver of the river” because they filter harmful substances like algae from bodies of water. But the species, once found in abundance in Central Texas, have declined in recent years due to population growth and development destroying its habitat.

In its ruling, the agency also designated 1,577 miles of rivers and creeks in the Colorado, Guadalupe, Brazos and Trinity river basins as critical habitat or an area important to the species’ conservation and recovery. The designation bans development or projects that could harm the species and requires a federal permit or license, unless the permit seeker works with the Fish and Wildlife Service to modify their projects to protect the endangered species.

Texas is home to more than 50 species of native freshwater mussels. The new rule adds the Guadalupe fatmucket, Texas fatmucket, Guadalupe orb, Texas pimpleback, Balcones spike, and false spike to the endangered listing, meaning the species is in danger of extinction. The Texas fawnsfoot is receiving a threatened listing, which means it is likely to become endangered in the future.

Experts say this designation will result in cleaner rivers, streams and creeks.

“[Freshwater mussels] really are foundational keystone species in any river system,” said Shaun Donovan, a manager of environmental sciences at the San Antonio River Authority.

Donovan has worked for years on mussel conservation efforts in San Antonio. Most recently, he worked with other biologists and scientists to reintroduce mussels to the region’s river basin. He describes the freshwater mussels as living rocks.

Freshwater mussels eat algae and other bacteria, which helps clean water systems. According to the Wildlife Service, a single freshwater mussel can pump and filter between eight and 15 gallons of water per day, making them some of the most powerful filters in watersheds.

This article was written by  ALEJANDRA MARTINEZ of The Texas Tribune .  This article originally at :