The alarming wildlife population declines, those happening especially in marine and freshwater ecosystems, have a new suspect: vitamin deficiency, specifically thiamine (Vitamin B1) deficiency. Thiamine is one of the eight essential B vitamins used in critical metabolism processes – for example, nervous system functioning and energy production. Thiamine is mainly produced by plants, phytoplankton, bacteria, and fungi. Animals, as well as people, must obtain it through their diets.
A modest, but growing body of research is asking an eerie question – can a vitamin crucial for supporting life disappear from a food chain? Some scientists think so and diligently study the still largely unknown but potentially alarming phenomenon.
From 2004 to 2009, Lennart Balk, an environmental biochemist at the University of Stockholm, Sweden, witnessed a strange paralytic disease occurring in seabirds along the Baltic Sea coast. Suddenly, many birds in the previously thriving colonies couldn’t fly or eat, had difficulty breathing, and some were completely paralyzed. By 2009, his team documented the symptoms in the European herring gulls (Larus argentatus), the common eider (Somateria mollissima), and the theon starling (Sturnus vulgaris) on sites across northern Europe.
To prove the theory on the biochemical level, Balk and his researchers tested thiamine concentrations in Larus argentatus egg yolks and found that it was 41% lower in birds from the Baltic Sea than in specimens coming from the Iceland region. Next, they treated sick birds with thiamine injections. Nine out of ten herring gulls recovered over a two-week period, while the untreated birds showed no improvement.
In the 1990s, Balk has documented a similar event in several Baltic fish species- the Atlantic salmon (Salmo salar) had produced larvae that were lethargic and couldn’t swim straight before dying. Experimentally treated with thiamine, almost all survived. In 2016, he showed that several other species across northern Europe, including blue mussels (Mytilus sp.) and eels (Anguilla sp.), were also suffering from the deficiency.
Lennart Balk wasn’t the only scientist noticing this. Since 1995, John Fitzsimons, a now-retired Canadian government fish biologist, and other researches had documented thiamine deficiency in lake trout and several salmon species in the Great Lakes, with symptoms similar of those seen in Balk’s Baltic sea fish. The tests excluded pollution as a potential factor, and like in the Balk’s experiment, the symptoms could be reversed by using the thiamine treatment.
Don Tillitt, an environmental toxicologist at the USGS, discovered the same phenomenon in Michigan in 2005 and reported that salmon and lake trout were eating mainly alewives (Alosa pseudoharengus), an invasive species of fish that is rich in thiaminase- an enzyme which breaks down thiamine. “Thiamine deficiency almost completely stopped all reproduction in some fish species in the Great Lakes, causing huge population declines,” Tillitt says.
Though the researches haven’t pinpointed the reasons for the nutrient’s disappearance, the problem is probably multifold. In the case of Tillitt’s salmons and trouts, eating the thiaminase-rich invasive prey obviously triggered the deficiency. However, other cases are not so easy to solve, and it is not clear why thiamine is lacking. Options are many: from a hypothesized pollutantwhich blocks the vitamin’s absorption, tosea warmingcaused by climate change.
One of the very plausible theory is that sea warming is causing imbalances on the microscopic level. Phytoplankton and bacteria, the primary producers of thiamine and other B vitamins, could be starved of vitamins bytoxic algae and cyanobacteria blooms. The rapidly proliferating bacteria could use up the vitamin before phytoplankton, spiraling the deficiency further up in the food chain.
Sergio Sañudo-Wilhelmy,anenvironmental biogeochemist at the University of Southern California, Los Angeles,has measured very low levels of the B-group vitamins, including thiamine in California’s coastal waters. Other scientists found similar depletions in some parts of the open ocean. Unfortunately, the data on dissolved vitamin content across regions and seasons are limited, so it is hard to come up with patterns of environmental vitamin levels to compare the new data with.
Critics of the deficiency theory imply that Balk’s studies have failed to exclude botulism, a relatively common periodic occurrence in seabirds, which shows similar symptoms. However, botulism could hardly explain the success in treating the diseased birds with thiamine.
While the cause remains a mystery, solutions to some of the cases of wildlife vitamin deficiency do exist. The clear deficiency in alewives-eating salmon of the Great Lakes, thiamine was added to the water in fish hatcheries. Then, the thiamine-boosted fish were then released into the lakes. As the populations started to recover, the alewives’ numbers started to decline, and unhindered reproduction of trout and salmon continued naturally.
For other cases, cyanobacterial and algal blooms could be made less severe by cutting down on the fertilizer runoff pollution. Toxic blooms cause a lot of damage on multiple levels, so this is certainly one of the steps that would benefit wildlife and entire ecosystems in numerous ways, as well as human societies. Based on his research that spans for decades, Balk concludes that “The most important thing to do is to find the cause.”
Gilbert, N. 2018. News Feature: Deadly deficiency at the heart of an environmental mystery. PNAS https://www.pnas.org/content/115/42/10532