Nav: Home

Spinal deformities in Sacramento-San Joaquin delta fish linked to toxic mineral selenium

February 24, 2020

Native fish discovered with spinal deformities in California's Sacramento-San Joaquin Delta in 2011 were exposed to high levels of selenium from their parents and food they ate as juveniles in the San Joaquin River, new research has found.

The finding published in Environmental Science and Technology indicates that some fish in the region may experience harmful levels of selenium. Selenium is a naturally occurring mineral that is essential to life but turns toxic and can cause deformities at high levels. Deformities were also found in birds exposed to selenium concentrated in agricultural runoff in the same area in the 1980s.

Biologists collected the juvenile fish, minnows known as Sacramento splittail, from a pumping station in the Sacramento-San Joaquin River Delta in 2011. They soon realized that more than 80 percent of the approximately 1,000 collected fish exhibited spinal deformities.

"This was not just a few fish, it was the majority of them," said Fred Feyrer, a research fish biologist at the U.S. Geological Survey's California Water Science Center and co-lead of the research.

Clues from Ear Bones

Scientists raised the fish in tanks for several years. In the meantime, they developed laboratory methods to examine the ear bones of the fish for clues about where they had encountered the selenium. Called otoliths, the ear bones record chemical traces of the conditions the fish experience as they grow.

"We found that the otoliths record a diary of selenium exposure from birth to death, and were the key to unraveling this mystery," said Rachel C. Johnson, a research biologist at NOAA Fisheries' Southwest Fisheries Science Center and University of California Davis and lead author of the research.

Researchers used high-intensity X-rays at Cornell University's Cornell High Energy Synchrotron Source to measure selenium concentrations in the otoliths. They revealed that the fish had absorbed selenium from their mothers, and while feeding as juveniles in the San Joaquin River. "They got it from both directions," Johnson said.

Another recent study by the same authors found high concentrations of selenium in some adult splittail feeding in the San Francisco Estuary. The concentrations exceeded protective criteria set by the U.S. Environmental Protection Agency. Splittail feed heavily on Asian clams, which concentrate selenium while filter feeding. The fish then pass the selenium on to offspring in the yolk of their eggs.

The details of how the fish encountered the selenium could help determine what to do about it, said Robin Stewart, a research hydrologist at the U.S. Geological Survey and coauthor of the research.

"These tools that help us understand where and how it happens will also help inform management agencies how they might best reduce risk," she said.

Rarely Seen in Wild

The findings raise the question of whether other fish such as salmon also encounter elevated levels of selenium, Johnson said. Scientists rarely see toxic effects of selenium in the wild. Regardless of how often it happens, afflicted fish either die or are quickly consumed by predators.

Sacramento splittail exist only in the Sacramento-San Joaquin Delta, and grow more than a foot long as adults. They reproduce most abundantly in wet years such as 2011, when rivers spread into adjacent floodplains and open new habitat to fish. One question remains: do fish such as the splittail encounter high levels of selenium only in such wet years when the floodplain habitat is available, or more commonly?

"Was this a one-time event?" Stewart asked. "What we don't know is how frequently this could be happening, because no one is out there looking for these fish before they disappear."
-end-
Coauthors of the research represent NOAA Fisheries; U.S Geological Survey; State University of New York College of Environmental Science and Forestry; University of California, Davis; and Cornell University.

NOAA Fisheries West Coast Region

Related Selenium Articles:

Stream pollution from mountaintop mining doesn't stay put in the water
Since the 1980s, a mountaintop mine in West Virginia has been leaching selenium into nearby streams at levels deemed unsafe for aquatic life.
Spinal deformities in Sacramento-San Joaquin delta fish linked to toxic mineral selenium
Native fish discovered with spinal deformities in California's Sacramento-San Joaquin Delta in 2011 were exposed to high levels of selenium from their parents and food they ate as juveniles in the San Joaquin River, new research has found.
Agricultural area residents in danger of inhaling toxic aerosols
Excess selenium from fertilizers and other natural sources can create air pollution that could lead to lung cancer, asthma, and Type 2 diabetes, according to new UC Riverside research.
It's a small (coal-polluted) world, after all
A study published in Environmental Toxicology and Chemistry underscores that the release of pollutants in one region can have implications beyond its borders; emphasizing the dire need for global collaboration on environmental issues.
Russian scientists studied the effect of selenium on the properties of basil
Today many agricultural plants are grown using hydroponics, i.e. in artificial soilless environments.
Turning to old remedies for new health challenges
The last thing anyone wants during a stay in the hospital is a hospital-acquired infection.
Selenium anchors could improve durability of platinum fuel cell catalysts
Researchers at the Georgia Institute of Technology have developed a new platinum-based catalytic system that is far more durable than traditional commercial systems and has a potentially longer lifespan.
Researchers gain key insight into solar material's soaring efficiency
In collaboration with partners at Loughborough University in the United Kingdom, researchers at CSU's National Science Foundation-supported Next Generation Photovoltaics Center have reported a key breakthrough in how the performance of cadmium telluride thin-film solar cells is improved even further by the addition of another material, selenium.
Selenium protects a specific type of interneurons in the brain
Exactly 200 years after the discovery of the trace element selenium, researchers at Helmholtz Zentrum München have shown for the first time why this chemical element is indispensable for mammalian life.
How selenium compounds might become catalysts
Chemists at Ruhr-Universitat Bochum have tested a new approach for activating chemical reactions based on the element selenium.
More Selenium News and Selenium Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Clint Smith
The killing of George Floyd by a police officer has sparked massive protests nationwide. This hour, writer and scholar Clint Smith reflects on this moment, through conversation, letters, and poetry.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.