March 7, 2002 (4:30 PM)
Hay’s Spring Amphipod
Stygobromus hayi
SPECIES CODE: K004 I01
STATUS:
Endangered throughout its range- U.S.A. (DC) (47 FR 5425, February 5, 1982).
SPECIES DESCRIPTION: This
small aquatic amphipod is commonly referred to as
REPRODUCTION AND DEVELOPMENT: Some females have
been collected with brood plates, but egg-bearing females have not been found
(Nature Serve Explorer 2002).
RANGE AND POPULATION LEVEL: Hay’s Spring
amphipod is only known from one population inhabiting an underground aquifer in
an urban area. The animal has been
collected from a single spring at the south end of National Zoological Park,
Washington, D.C. and at four other locations within Rock Creek Park, which
adjoins the National Zoo (Pavek 2002).
These three collection sites lie in close proximity to each other. The National Zoological Park spring emerges
from the rocky western wall of Rock Creek Valley and flows about 35 m into Rock
Creek. The portion of the spring inhabited by Hay’s Spring
amphipod is less than 1 meter wide. The extremely small size of this habitat
makes the species exceptionally vulnerable to construction activities, which
have drastically reduced the number of springs in Washington (Williams
1977). The size of the population(s) of
the crustacean is unknown. Except for the outlet, the aquifer is largely
inaccessible. No more than ten individuals have been seen at any one time (Nature
Serve Explorer 2002).
HABITAT: The Hay’s spring
amphipod inhabits a ground water outlet that feeds into a low gradient
creek. Precise data on this habitat is
lacking due to inaccessibility of habitat (Nature Serve Explorer 2002).
PAST THREATS: Survival of this aquatic crustacean has been
threatened by modification of its habitat by flooding and construction
activities and by over collection for scientific purposes.
Usually high flood levels from Rock
Creek reach the level of the spring habitat of Hay’s Spring amphipod. This level has been flooded with
increasing frequency in recent years (CHM Hill 1979). Flood waters may
adversely affect the spring habitat by removing individual amphipods, as well
as the leaves and soft bottom sediments that form their microhabitat, from the
spring.
Construction activities, if not
carefully carried out, could adversely affect or eliminate the spring habitat.
Such activities have eliminated most of Washington’s springs during the last 100 years (Williams 1977).
Although a small fence now surrounds the spring, the significance of this
structure could easily be overlooked during parking lot construction. The
spring is so small that careless movement of equipment slightly onto the
hillside from which the spring flows could have a catastrophic effect on the
habitat.
CURRENT THREATS: The
small size of the species’
population and habitat, as well as the fragile nature of the habitat, makes the
species vulnerable to flooding, isolated acts of vandalism, and construction or
maintenance accidents that might harm or destroy the crustacean’s habitat (USFWS 1982).
Possible additional threats include groundwater contamination or flow
alteration caused by further urban development (Nature Serve Explorer
2002). The urban area surrounding the
park poses potential risks due to toxic spills (such as oil and gas), nonpoint
source inputs (such as fertilizers and pesticides), land disturbances, sewer
leaks, and excessive stormwater flows that might adversely affect groundwater. Except for parklands, additional potential
habitat where Hay’s Spring amphipod populations may have
occurred in the District has largely been lost to development (Pavek 2002).
CONSERVATION MEASURES:
LITERATURE CITED:
CHZM Hill. 1979. Draft Rock Creek
Watershed Conservation Study. Prepared for Department of the Interior, National
Park Service.
Nature Serve Explorer. An online encyclopedia of life [web
application]. 2001. Version 1.6.
Arlington, Virginia, USA: Nature Serve.
Available: http://www.natureserve.org/explorer (Accessed: March 6, 2002).
Pavek, D. 2002.
Endemic Amphipods in our Nation’s
Capital. Endangered Species
Bulletin. 27 (1): 8-9.
U.S. Fish and Wildlife Service.
1982. Endangered and Threatened Wildlife
and Plants; Listing Hay’s Spring
Amphipod as an Endangered Species. 47
Federal Register 5425.
Williams, G. P. 1977. Washington, D.C.‘s vanishing springs and waterways. Geological Survey Circular 752.