The effect of selenium toxicity on wildlife has been known for more than 50 years. This issue drew particular attention in the 1980s when embryo deformity and mortality was observed in birds at a wildlife refuge in California. Harmful effects from selenium were determined to be connected to irrigation drainage water.
As a result, an effort began to monitor levels of selenium in irrigation drainage water throughout the western United States. One location, studied by both the U.S. Geological Survey and U.S. 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.
In the past decade, Salton Sea water elevation has declined due to drought, the lining of canals, and changes in the 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 selenium and related metals needs to be assessed. This study will help evaluate whether such wetlands are suitable for migratory and endangered birds.
The initial phase of this work consisted of a data compilation and review assessment of selenium in the Salton Sea region. This work gathered more than 7,000 measurements of selenium in water, sediment, and biota. The information was then compiled into two data releases for ease of access. A forthcoming scientific investigations report (SIR) will further evaluate these data.
The SIR will also be used to develop a phased study plan designed to assess potential selenium risks to the federally endangered bird species, the Yuma Ridgway’s Rail (Rallus obsoletus yumanensis) in wetlands around the southern part of the Salton Sea.
Approach and Timeline
The first phase of this work (Phase I) consisted of pilot work that is now complete. This pilot work was designed to inform more detailed sample collection in the second phase (Phase II). Phase II is now ongoing. The data from the first two phases will then be used in phase three (Phase III) – a selenium risk assessment model for the Yuma Ridgway’s Rail.
Phase I sampling was done in 2021 and 2022; Phase II started in January 2023 and is ongoing. Phase III is anticipated to start in late 2024.
Science Plan
This study uses different water sources and strategies to gather information on selenium in selected wetlands. Water and sediment data collection focuses on selenium, nutrients, and associated trace elements. These data will provide information on how selenium may move from dissolved forms in the inflowing drain water into forms that may find their way into wetland food webs.
Water and sediment sample collection is tightly paired with biological sample collection at the base of wetland food webs. This includes Yuma Ridgway’s Rail sampling by the USGS cooperative research unit at the University of Idaho. We will use this information to better understand selenium within these dynamic wetland environments. These data will help determine whether the wetlands are viable long-term habitats for perennial and migratory wildlife.
Results and benefits
Data collected in this project will be compiled in one or more data releases. Risk assessment modeling will be outlined in an interpretive report. The report will assess the selenium information collected in Phase I and Phase II. Prior to publication of the report, several stakeholder meetings will be held with federal, state, and local partners in Coachella and Imperial Valleys. The aim of these meetings will be to outline the report’s findings. These data will serve in the guidance of managements decisions regarding the ecology and long-term sustainability of Salton Sea wetlands.
The effect of selenium toxicity on wildlife has been known for more than 50 years. This issue drew particular attention in the 1980s when embryo deformity and mortality was observed in birds at a wildlife refuge in California. Harmful effects from selenium were determined to be connected to irrigation drainage water.
As a result, an effort began to monitor levels of selenium in irrigation drainage water throughout the western United States. One location, studied by both the U.S. Geological Survey and U.S. 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.
In the past decade, Salton Sea water elevation has declined due to drought, the lining of canals, and changes in the 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 selenium and related metals needs to be assessed. This study will help evaluate whether such wetlands are suitable for migratory and endangered birds.
The initial phase of this work consisted of a data compilation and review assessment of selenium in the Salton Sea region. This work gathered more than 7,000 measurements of selenium in water, sediment, and biota. The information was then compiled into two data releases for ease of access. A forthcoming scientific investigations report (SIR) will further evaluate these data.
The SIR will also be used to develop a phased study plan designed to assess potential selenium risks to the federally endangered bird species, the Yuma Ridgway’s Rail (Rallus obsoletus yumanensis) in wetlands around the southern part of the Salton Sea.
Approach and Timeline
The first phase of this work (Phase I) consisted of pilot work that is now complete. This pilot work was designed to inform more detailed sample collection in the second phase (Phase II). Phase II is now ongoing. The data from the first two phases will then be used in phase three (Phase III) – a selenium risk assessment model for the Yuma Ridgway’s Rail.
Phase I sampling was done in 2021 and 2022; Phase II started in January 2023 and is ongoing. Phase III is anticipated to start in late 2024.
Science Plan
This study uses different water sources and strategies to gather information on selenium in selected wetlands. Water and sediment data collection focuses on selenium, nutrients, and associated trace elements. These data will provide information on how selenium may move from dissolved forms in the inflowing drain water into forms that may find their way into wetland food webs.
Water and sediment sample collection is tightly paired with biological sample collection at the base of wetland food webs. This includes Yuma Ridgway’s Rail sampling by the USGS cooperative research unit at the University of Idaho. We will use this information to better understand selenium within these dynamic wetland environments. These data will help determine whether the wetlands are viable long-term habitats for perennial and migratory wildlife.
Results and benefits
Data collected in this project will be compiled in one or more data releases. Risk assessment modeling will be outlined in an interpretive report. The report will assess the selenium information collected in Phase I and Phase II. Prior to publication of the report, several stakeholder meetings will be held with federal, state, and local partners in Coachella and Imperial Valleys. The aim of these meetings will be to outline the report’s findings. These data will serve in the guidance of managements decisions regarding the ecology and long-term sustainability of Salton Sea wetlands.