Thursday, June 7, 2007 - 10:45 AM
383

Aquatic Community Composition in Ephemeral Stream Ecosystems in the Southwestern United States

Jeniffer S. Lynch, Grant DeJong, Lareina Wall, and Steve Canton. Chadwick Ecological Department, GEI Consultants, Inc., 5575 S. Sycamore St., Suite 101, Littleton, CO 80120

Aquatic communities were characterized at fifteen ephemeral stream sites within the Santa Cruz River, Rio Puerco, and Huerfano River watersheds, located respectively in Arizona, New Mexico, and Colorado.  The purpose of the study was to provide preliminary data on taxa composition of these ecosystems within the arid southwest.  Sampling of microinvertebrate and macroinvertebrate populations was conducted at each site following a precipitation event and continuing daily until water was no longer present.  Results of this study indicate that a limited number of taxa inhabit ephemeral streams in the arid southwest.  Few truly aquatic microinvertebrates were collected, and of these, most have the ability to persist in a cryptobiotic state, allowing them to survive the drought conditions that would periodically occur in ephemeral streams.  Aquatic macroinvertebrate populations were more diverse but still limited.  Most macroinvertebrate taxa collected had aerially dispersing life stages, likely accounting for their presence at these sites.  Cluster analysis results showed low similarity in macroinvertebrate taxa composition between watersheds, as most taxa were collected from only a single study area.  Further study of the aquatic communities of ephemeral streams is warranted, and should include the expansion of the geographic area to involve other ephemeral stream ecosystems.  

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