Selenium Hazard in the Salton Sea Environment, Summary of Current Knowledge to Inform Future Science

Science Center Objects

The effect of selenium (Se) toxicity on wildlife has been known for more than 50 years. The threat of Se contamination gained greater attention from federal agencies in the 1980s due to the observation of embryo deformity and mortality in birds at a National Wildlife Refuge in California. Harmful effects from Se were determined to be connected to irrigation drainage water.

As a result, an effort was begun to monitor levels of Se in irrigation drainage water throughout the western United States, including California. One area studied by both the US Geological Survey and Fish and Wildlife Service was the Salton Sea and its surrounding area. The Salton Sea is a shallow, saline, drainage lake at the southern end California. It lies between, and within, the Imperial and Coachella valleys.

Drain carrying runoff from farm fields in Imperial Valley

Drain carrying runoff from farm fields in Imperial Valley at the south end of the Salton Sea.  Runoff can contain relatively high concentrations of Se.

In the past decade, Salton Sea water elevation has declined due to drought, lining of canals, and changes to management of the Colorado River. This has resulted in the creation of new wetlands caused by drains and rivers no longer reaching the Salton Sea. Because these wetlands are new, the effect and possible toxicity of levels of Se and related metals, needs to be assessed. This study will help evaluate whether such wetlands are suitable for endangered aquatic and avian wildlife (fish and birds).

Science Plan

Though previous studies have shown that Salton Sea wildlife is susceptible to Se toxicity, these risks are not yet fully understood. Se concentrations from the Salton Sea and its surrounding area have not been fully evaluated for at least 20 years, since water levels in the Salton Sea have declined. New data needs to be put into context with past measurements to determine future risk to wildlife. Because of changes in the Salton Sea's water elevation and the creation of new wetlands, the effects of Se toxicity on aquatic and avian wildlife must be reassessed.

In this study, USGS scientists will examine past publications about Se and the Salton Sea.  By surveying these data and looking for correlations and trends, they will determine what gaps exist. A new study will then be conducted to sample Se and other trace element concentrations in water, sediment and wildlife. These data will help determine whether the wetlands are viable long-term habitats for perennial and migratory wildlife.

Newly formed wetland that formed as the Salton Sea level lowers

Newly formed wetland that formed as the Salton Sea level lowers.  The plants shown are likely less than 10 years old.  These new unmanaged wetlands provide habitat for aquatic and avian life, but the water quality of these wetlands is currently unknown, and the ability of these wetlands to provide a long-term habitat for endangered Yuma Ridgeway’s Rail and Desert Pupfish is unknown. Inset shows picture of a Yuma Ridgeway’s Rail.

Objectives and Approach

The objective of this study is to provide a summary of previous research on Se that has been conducted in the Salton Sea area that can be used for assessing the hazards of Se to aquatic and avian wildlife birds, particularly the endangered Desert Pupfish and Yuma Ridgway’s Rail.  The collected data will be used to assess the hazard that newly created wetlands may pose to such wildlife, and identify additional information needed to accomplish or improve future risk assessments.

To accomplish these objectives, scientists will review existing scientific information on concentrations of Se and related elements and compounds in Salton Sea water, sediment and aquatic and avian wildlife. From this information, scientists will determine if concentrations have changed over time and what future risks might be.  

Results and benefits

The product for this report will be a Scientific Investigations Report that will assess the Se information that is available for the Salton Sea and assess the risks and gaps in these data.  Several stakeholder meetings will be held with federal, state, and local partners in Coachella and Imperial valleys to outline the findings from the report before it is published.  These data will then be used to inform future research and eventually serve in the guidance of managements decisions regarding the ecology of Salton Sea wetlands.