In an April 1, 2024 letter to three water boards, fishing and conservation groups and the Winnemem Wintu Tribe urged regulators to control recently measured excess levels of selenium in Mud Slough.
Mud Slough drains selenium-impaired land on the west side of the San Joaquin Valley into the San Joaquin River and ultimately San Francisco Bay.
The letter was signed by Stephan C. Volker, Attorney for the California Sportfishing Protection Alliance (CSPA), Pacific Coast Federation of Fisherman’s Associations (PCFFA), the Institute for Fisheries Resources (IFR), SFCBOA, North Coast Rivers Alliance (NCRA) and Winnemem Wintu Tribe.
“The Mitigated Negative Declaration for the Mud Slough Project did not analyze the water quality impacts of routing Mud Slough flows to wetlands,” the letter stated. “No explanation is provided in the Mitigated Negative Declaration or the Grassland Bypass Project WDR as to why China Island State Wildlife Area and Newman Lake wetlands are not afforded the same protective water quality objective of 2 μg/L selenium, monthly mean as are Salt Slough and the Grasslands wetland supply channels.”
Selenium has long been known to cause reproductive failure, deformities, and death in fish and waterfowl, according to a statement from the California Sportfishing Protection Alliance (CSPA).
“Our groups have spent over a decade at the water boards and in court trying to bring runoff from Mud Slough into compliance with water quality standards,” said Chris Shutes, Executive Director of the California Sportfishing Protection Alliance. “Past selenium discharges accumulated in downstream waters, impacting fish and causing deformities. The water boards need to act to protect fish and wildlife from this toxic pollutant.”
”Previous action by the water boards limited discharges of water from Mud Slough to San Joaquin Valley wildlife refuges. It required the San Luis and Delta-Mendota Water Authority to instead supply the refuges with better quality groundwater,” Shutes continued.
“However, a new plan would resume delivery of water from Mud Slough to the refuges. Considering the history of waterfowl deformities in San Joaquin Valley refuges due to selenium contamination, the proposed change in source water is particularly alarming,” he argued.
San Joaquin Valley wildlife refuges are part of the Pacific Flyway. Birds that stop in these refuges migrate as far away as Alaska, noted Shutes.
The letter cites a 2018 study which found that selenium deformed Sacramento splittail, a native fish, in the San Joaquin River. It calls on regulators to strengthen the standards for selenium pollution, beginning with a wet-year monitoring program of splittail funded by the Water Authority.
“More broadly, the letter calls on the board to enforce existing protective standards for wetlands and to adopt more protective standards consistent with the findings of the EnvironmentalProtection Agency of what is necessary to protect fish and wildlife,” concluded Shutes.
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, according to the USGS: www.usgs.gov/...
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, published Feb. 24, 2020, in the journal Environmental Science & Technology: Lifetime Chronicles of Selenium Exposure Linked to Deformities in an Imperiled Migratory Fish.