Black Rock Playa, northwestern Nevada: physical processes and aquatic life

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The Black Rock Playa is affected by a multitude of processes, and flooding is one of the more important. Black Rock Playa floods occur every few years or sometimes more frequently. When the playa does not flood for a few years or more in a row, the surface can transform from a hard, durable surface to one that is soft and loose. During periods of frequent flooding and when the playa surface is firm, minimal wind-driven erosion occurs. Enhanced wind erosion likely occurs when the playa surface is soft and loose. This enhanced erosion occurs naturally but may be exacerbated by human activities that disrupt the fragile crust found on the playa when it is in its soft state. Playas are harsh environments for aquatic life because they are infrequently flooded by turbid, saline, and alkaline water that is followed by drought that may last many years. When flooded, playas support phytoplankton, bacteria, other microbes, and crustaceans that are a rich food resource for migrating birds. Most of the aquatic species on the Black Rock Playa are branchiopods—including fairy shrimp, tadpole shrimp, and water fleas. All of these animals have a common life history where eggs lie encased in dry playa soil and do not hatch until the playa is flooded for enough time for adults to grow and reproduce. Recreational use of the Black Rock Playa by vehicles and long-term camping decreases branchiopod egg abundance. In playa systems, the effect of human use on branchiopod populations is likely to be greatest when 1) areas of the playa with highest egg density are impacted, 2) large portions of playa are affected, 3) frequency of reproduction is reduced by lengthy periods between inundation, and 4) egg abundance declines due to years of cumulative activity between inundations. The effects of use on the Black Rock Playa also may be compounded by annual, incremental transition from a hard, consolidated playa immediately following inundation to an increasingly soft and loose playa. Use of the Black Rock Playa has increased during the past 25 years, and it is now annually visited by tens of thousands of people and thousands of vehicles. The most intense use is focused at Black Rock City, which covers only three percent of the playa. Other uses are comparatively short-term and involve fewer people, but their impact on branchiopods may be equivalent because these activities disturb a much greater area than Black Rock City.

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ELECTRONIC FILE - Zoology

SWAP citation (02/19/16):
Adams KD, Sada DW. 2010. Black Rock Playa, northwestern Nevada: physical processes and aquatic life. [place unknown]: Desert Research Institute. [accessed 2016 Feb 13]. http://www.spatial-ed.com/images/documents/Projects/Burning_Man/BlackRoc...