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 Searching for rare crustaceans called amphipods, scientists with American University pour springwater through a fine mesh. The survey, conducted in 2001, revealed a big surprise: Rock Creek Park in Washington, D.C., hosts a diverse group of the tiny animals, including Kenk’s amphipod. Information from the survey will also help the National Park Service protect the unusual park habitat. American University, Irena Sereg Diane Pavek
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 By Diane Pavek Rock Creek Park is not only an oasis for visitors within the concrete and asphalt sprawl of the nation’s capital but it is also a refuge for freshwater crustaceans called amphipods (in the genus Stygobromus). Given its urban location, it was surprising to discover in 2001 that Rock Creek Park, a natural area of 1,754 acres (701.6 hectares), has one of the most diverse Stygobromus assemblages in perched, small-basin habitats anywhere in the United States. Two species in the park are federally endangered and rare: Hay’s Spring (Stygobromus hayi) and Kenk’s amphipods (S. kenki), respectively. Hay’s Spring amphipod is known from five sites and Kenk’s amphipod from four sites, all within the District of Columbia. Rock Creek Park, established in 1890 as the third national park, protects many miles of Rock Creek tributaries within the D.C. area. However, outside of park boundaries, large portions of the tributaries in the Rock Creek watershed have been converted to covered sewers or filled in with rocks and soil. Discoveries made in 2001 about the unique Stygobromus fauna in Rock Creek Park emphasize both the importance of urban parks as significant biological refuges and the value of parks as natural laboratories. American University scientist Dr. David Culver is completing an amphipod species inventory at multiple springs in Rock Creek Park. He used chemical and physical analyses of the water and sediment to describe the spring and seep sites where amphipods live and to investigate current threats to their habitats. Dr. Culver will provide management and protection recommendations to the National Park Service based on the results of his study. Typically, exclusively subterranean aquatic species such as Stygobromus occur in caves or permanent groundwater habitats where shallow fissures or cavities are isolated in the bedrock and have low levels of organic matter. However, Dr. Culver found that three of the Stygobromus species in the Rock Creek valley live in habitat that is shallow, subsurface, high in organic matter, and possibly seasonally dry. That Stygobromus could be found in these conditions was not suspected before this year’s work in the park. The habitat is called hypotelminorheic and is created when groundwater seeps to the surface from underlying bedrock to flow up through sediments and vegetative litter. In Rock Creek Park, thick layers of clay lie beneath these seeps, stopping the water and creating perched pockets of subterranean habitat for the Stygobromus. Ascertaining the security of the amphipod populations and mitigating any identified threats is important. Correlations between habitat characteristics and presence or absence of amphipods may help explain species distributions in the park. Preliminary results from the chemical analyses of sediment at three of the spring sites revealed elevated levels of some heavy metals. One seep where Kenk’s amphipods occur had significantly lower levels of selenium compared to a seep where the amphipods do not occur. Further analyses of the data are ongoing. Currently, the extent of the aquifers that feed the springs and seeps is unknown and a hydrogeologic study is needed to fully understand protection at the watershed level. Beyond the park’s borders, the Maryland Department of Natural Resources is currently searching for Kenk’s amphipod within that state. Partnerships with other agencies and universities are essential to fully describe the distribution and habitat of these rare subterranean amphipods. Exploring the conservation capacity of small parks has proven important for enhancing the scientific understanding of species like amphipods. In turn, science makes it increasingly clear that small natural areas like Rock Creek Park are ecological remnants that protect a range of habitats and species that may no longer exist in the surrounding urban environment. |
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This material is from Natural Resource Year in Review--2001, published by the National Park Service, U.S. Department of the Interior, in May 2001 (publication D-2255) /YearInReview/yir/yir2001/03_laboratories/03_1_pavek.html Last Updated: |
