Stygobromus hayi is a rare species of crustacean known by the common name Hay's Spring amphipod. It is endemic to the District of Columbia in the United States, where it occurs only in Rock Creek, a tributary of the Potomac River. It is a federally listed endangered species, is listed as Endangered on the IUCN Red List, and as Critically Imperiled by NatureServe.
One of three amphipods that are found only in the District of Columbia, this species has been called "Washington D.C.'s most famous endemic." Hay's spring amphipod lives in five springs along Rock Creek, occurrences which make up a single population. All the sites are located in a three-mile stretch of the creek. The amphipod lives in seeps formed when water rises through the substrate and is then trapped just under the ground surface by a clay layer.
This amphipod measures 10 millimeters (0.39 in) in length. Because it lives underground, it is white in color and eyeless.
This species is threatened by the degradation of its urban habitat. Heavy metals have been detected in the area. Other forms of pollution could occur, such as oil spills, sewer leaks, and fertilizer runoff. Flooding may destroy individuals and remove the microhabitat they inhabit. Construction nearby may damage the creek. Recreational activity next to the creek may increase the likelihood of pollution.
- Pavek, D. Urban refuge for rare amphipods in the National Capital Region. Natural Resource Year in Review 2001. National Park Service.
- USFWS. Stygobromus hayi Five-year Review. December 2007.
- Inland Water Crustacean Specialist Group (1996). "Stygobromus hayi". IUCN Red List of Threatened Species. Version 2.3. International Union for Conservation of Nature. Retrieved August 26, 2011.
- Stygobromus hayi. The Nature Conservancy.
- Pavek, D. Endemic amphipods in our nation's capital. Endangered Species Bulletin Jan-Feb 2002.