Recent
investigations have documented degraded water quality conditions in Las
Vegas Wash and Lake Mead. The degradation of water quality has adversely
affected the quality of fish and wildlife habitat associated with Las
Vegas Wash and Las Vegas Bay, Clark County, Nevada. Contaminant accumulation,
tissue abnormalities, and evidence of reproductive effects (endocrine
system disruption) have been identified in fish from Las Vegas Wash and
Bay. In 1998, the U.S. Geological Survey (USGS) Biological Resources
Division and the U.S. Fish and Wildlife Service (Service) initiated a
joint investigation to assess implications of contaminants associated
with Las Vegas Wash. The investigation was expanded in 2000 to address
concerns specific to Department of the Interior trust resources.
The primary objective of the Service's components of the investigation
included:
Review existing data to assess the existence and degree of threats to
fish and wildlife;- Assess organochlorine compounds and trace elements in avian eggs;
- Assess razorback sucker exposure to endocrine disrupting compounds and other contaminants, and
- Assess the potential for downstream impacts to endangered fishes.
This study was initiated to assess the extent and magnitude of contaminant threats from Las Vegas Wash to Lake Mead and the Colorado River downstream of Hoover Dam. Concerns have been identified with low dissolved oxygen concentrations, elevated concentrations or nutrients, dissolved solids, major ions, and elevated bacterial counts in water from the lower Las Vegas Wash and portions of Las Vegas Bay. A variety of potentially toxic compound were identified in water and sediment, including metals, trace elements, perchlorate, pesticides, organochlorine compounds, dioxins, furans, polycyclic aromatic hydrocarbons, phthalates, phenolic compounds, and pharmaceutical and personal care products. Many of these contaminants were identified at levels known to be toxic to fish and wildlife. Elevated organochlorine compound concentrations were found in fish and avian eggs in the Las Vegas Wash and Bay area. Selenium was elevated in fish tissue throughout the study area. Observed biological effects include abnormal hormone concentrations and ratios and tissue damage in fish.
The
success of habitat restoration efforts is to design and implement restoration
efforts which do not increase contaminants exposure and effects in created
habitats or otherwise transfer contaminant threats to other areas and
other species. Effective monitoring then becomes critical to identifying
and avoiding adverse effects to fish and wildlife. As such, monitoring
programs, need to assess the occurrence and severity of all contaminants
and conditions of concern, including the presence of nonstandard contaminants
such as endocrine disrupting chemicals, pharmaceuticals and personal care
products, and toxic constituents associated with sewage effluent and urban
runoff. Similarly, monitoring efforts should include assessment
of habitat conditions and the diversity, abundance, health, and condition
of fish, wildlife, plants, and invertebrates.
Learn More by Reading the Full Report:Tuttle, P.L. and Orsak, E.L., Las Vegas Wash Water Quality and Implications to Fish and Wildlife, USFWS. Nevada FWO. 2001.
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