Thiamine deficiency might not be limited to the water, either. Balk says he has tested liver, brain, and blood samples from moose in southern Sweden and measured the levels of enzymes that correlate to thiamine activity. His results, he says, point toward “severe” thiamine deficiency.
In a 2016 paper, Balk and 20 coauthors sounded the alarm with a hypothesis that thiamine deficiency might be driving long-term wildlife-population declines. Their paper noted that “population sizes of both terrestrial and marine vertebrate species dropped by half” from 1970 to 2012, “and from 1950 to 2010, the global seabird population declined overall” by 70 percent. These downslides, the authors explained, are happening faster than what would be expected due to “known threats to biodiversity,” such as habitat loss.
By then, Balk and other scientists had clearly identified inadequate thiamine levels in species around much of the globe—but a root cause of the deficiency remained evasive.
“We’ve thought, It must be something in the air, or something in the water,” says Tracy Collier, a Seattle-based environmental toxicologist who has collaborated with Balk on thiamine-deficiency research.
Balk is equally mystified, but is confident that humans are to blame. The symptoms he has observed in thiamine-deficient animals are so severe, he explains, that if natural phenomena were the cause, affected animal populations would have vanished or adapted long ago. Balk believes that human activity is somehow sapping ecosystems of vitamin B1—either by blocking production or obstructing its passage from one trophic level to the next.
So does Dale Honeyfield, who worked with the U.S. Geological Survey as a research chemist and has studied thiamine deficiency since the mid-1990s.
“Humans are somehow involved,” he says. “Thiamine deficiency is really an indicator that we have an ecosystem that is disrupted.”
Scientists are floating various explanations for what’s depriving organisms of this nutrient. Some believe that changing environmental conditions, especially in the ocean, may be stifling thiamine production or its transfer between producers and the animals that eat them. Sergio Sañudo-Wilhelmy, a professor of biological sciences at the University of Southern California, says that warming ocean water could be affecting the populations of microorganisms that produce thiamine and other vitamins—potentially upsetting the basic chemical balances that marine ecosystems depend on.
“In different temperatures, different phytoplankton and bacteria grow faster,” he says.
This, he explains, could hypothetically allow microorganisms that don’t produce thiamine—but, instead, acquire it through their diet—to outcompete the thiamine producers, effectively reducing thiamine concentrations in the food web.
Such a mechanism could be why Sañudo-Wilhelmy and several other researchers, during a research project about a decade ago, found low levels of B vitamins, including thiamine, in water samples collected off the coast of Baja California.