Stygobromus hayi is a rare species of crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

 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

Rock Creek (Potomac River)

Rock Creek is a free-flowing tributary of the Potomac River, which empties into the Atlantic Ocean via the Chesapeake Bay. The creek is long, with a drainage area of about...

, a tributary of the Potomac River

Potomac River

The Potomac River flows into the Chesapeake Bay, located along the mid-Atlantic coast of the United States. The river is approximately long, with a drainage area of about 14,700 square miles...

. It is a federally listed endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

, is listed as Endangered on the IUCN Red List

IUCN Red List

The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...

, and as Critically Imperiled by NatureServe

NatureServe

NatureServe is a non-profit conservation organization whose mission is to provide the scientific basis for effective conservation action. NatureServe and its network of natural heritage programs are the leading source for information about rare and endangered species and threatened ecosystems in...

.

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

Spring (hydrosphere)

A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...

 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 seep

Seep

A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the earth's atmosphere and surface, normally under low pressure or flow. Seeps generally occur above either terrestrial or offshore petroleum accumulation structures...

s formed when water rises through the substrate and is then trapped just under the ground surface by a clay

Clay

Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

 layer.

This amphipod measures one centimeter in length. 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

Pollution

Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 could occur, such as oil spill

Oil spill

An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...

s, sewer

Sanitary sewer

A sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...

 leaks, and fertilizer runoff. Flood

Flood

A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

ing 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.

Rock Creek Park protects the creeks and its springs. Different agencies monitor the creek and its sensitive species, including this amphipod and its relative, Stygobromus kenki.