Toxic Mineral Selenium Found in California Fish Species

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Spinal deformities in California native fish species, the Sacramento Splittail, were first seen in the Sacramento-San Joaquin Delta in 2011. It is now known that this is due to exposure to the chemical element selenium. 

Sacramento splittail showing spinal deformities traced to exposure to selenium.

Sacramento splittail showing spinal deformities traced to exposure to selenium.​​​​​​​

Newly published research, by USGS and NOAA scientists, shows that the fish were exposed to high levels of selenium from both their parents and the food they ate as juveniles in the San Joaquin River.

Selenium (Se) is both an essential element and potent teratogen and its contamination is strongly tied to core economic activities (e.g., agriculture, mining, energy production). In the Sacramento-San Joaquin Bay-Delta, Se is concentrated primarily through the import of agriculturally irrigated salinized soils containing high levels of geologically derived Se in the San Joaquin Valley (and within estuary point-source loading from oil refining and wastewater treatment effluents) leading to elevated levels in fish and wildlife. How the movements of fish across the landscape influence Se exposure at different points during their life history has been difficult to resolve due to the complexity of the system and the diverse sources of Se.

For details on this research and its impacts, read the recent article in the journal Environmental Science & Technology: Lifetime Chronicles of Selenium Exposure Linked to Deformities in an Imperiled Migratory Fish.

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