Glaciers Are Disappearing and So Too Might the Microbial Ecosystems Within
(Inside Science) -- It was a hard hike up to the glacier. Pico Humboldt is the second-highest mountain peak in Venezuela and it'd taken three days for Andrés Yarzábal and his colleagues to make it to the top. They'd faced bad weather, strong winds and rocky terrain, but now the goal was close at hand. In front of them lay La Corona, also sometimes called Humboldt Glacier, one of the last two glaciers in the entire country.
The inspiration to visit these glaciers struck Yarzábal one day when he happened to glance up at them going out to his car. At the time, Yarzábal was working at the University of the Andes in Mérida, a mountain town in Venezuela nestled in the northern spur of the Andes Mountains. Yarzábal is a molecular microbiologist and is interested in extremophiles -- microbes that thrive in the world's hottest, coldest and most inhospitable environments. The glaciers around Mérida presented an attractive place to look for the hardy organisms.
Centuries ago, the glaciers had covered the mountain in a thick layer of ice. Mérida was once famous for nearby ski competitions and ice merchants. But by 2012, when Yarzábal mounted his first expedition, all that was left to greet him on the mountain were two small ice fields. Nevertheless, Yarzábal and his colleagues were triumphant, taking samples of the glacial ice -- samples they hoped would contain life.
"It was a really amazing adventure," said Yarzábal, now at the Catholic University of Cuenca in Ecuador.
Today, glaciers around the world face a peril similar to La Corona's: A warming world threatens to melt away them. If the glaciers vanish, so too might our chance to discover new knowledge and acquire new medical or agricultural tools from the life forms these unique landscapes support. In the meantime, scientists such as Yarzábal are rushing to harvest, document and understand glaciers' cold-resistant microbes before it's too late.
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A frozen home
Glaciers are essentially huge blocks of ice, frigid and foreboding, and we once thought of them as simply too extreme to harbor life. Now, however, we know they're not only habitable, but possibly one of the major ecosystems on Earth, considering they cover 11% of the Earth's land area. It's just that their denizens are tiny microbes.
New microbes may arrive at the glacier blown in by the wind or riding on dust particles or precipitation such as snowflakes. Over the slow march of time, natural selection and the extreme conditions will shape these new residents of the glacier to better fit their now home.
On the glacier's surface, for instance, some microbes may survive in small pools of liquid water, absorbing energy from the light of the sun. Others, whose ancestors were swept away from the surface by a stream of meltwater and sent plunging through crevasses and fissures to the dark, icy heart of the glacier, might eke out an existence lodged in the spaces between ice crystals, drawing chemical sustenance from the passing water. The meltwater stream may even reach the mountain's bedrock, where the weight and slow motion of the ice above grind the rock into powder, releasing enough nutrients to support an ecosystem that's never seen the sun.
In each of these environments, the microbes able to weather the cold will grow and evolve, developing new forms of critical enzymes or proteins that can work even in subzero environments. Adapted to their environment, they wouldn't only endure, but reproduce.
"They are not just surviving," said Alexandre Anesio, a biogeochemist at Aarhus University in Denmark who studies how glacial microbes grow and shape their icy environments. "They are growing, they are thriving." Some may evolve such that they're only ever found in ice -- as dependent on the glacier as a tropical plant is on a tropical forest. In fact, according to Anesio, a glacier is as much a biome as a forest or savanna. Just one with a paucity of lions and bears. Anesio, for his part, is particularly interested in the ecology of the glacier and is studying the microbes that live on the surface of the glacier, how they grow, and what may be limiting their growth.
There are many reasons that scientists study glacial organisms. Some researchers are looking into the threat of an ancient pathogen emerging from deep-freeze. Others look to glacial microbes as proxies for life forms we might find on other worlds. NASA has investigated microscopic life on the glaciers of Kilimanjaro, for instance. The thinking goes that if microbes could flourish in the heart of an earthly glacier, perhaps similar organisms may exist trapped in the glacial Martian poles or the icy moons of Jupiter.
One of Yarzábal's main reasons for studying glacial microbes is to see if they hold secrets that might help alpine farmers here on Earth.
Around Mérida, and indeed, much of the rest of the Andes range, the cold and factors like nutrient shortages can take a toll on crops' growth. Living microorganisms called biofertilizers can help plants thrive, but existing ones are often held back by the cold. Microbes from Mérida glaciers might produce compounds that would help plants survive and take in nutrients. If so, it could help boost agricultural production both locally and in other alpine environments, like those found in the Himalayas.
In a study, Yarzábal's team took four promising strains of bacteria from Mérida's glaciers and grew them in the lab. They then took wheat seeds and coated the seeds in a solution containing those bacteria, enrobing the seeds in a thin shell of microbes like a candy-maker would coat almonds in liquid chocolate.
These treated wheat seeds (along with a bacteria-free control group) were then sown in sterile soil in a temperature-controlled chamber. As a further challenge, the scientists did the same thing again, but also added a plant disease-causing pathogen to the soil. Would the glacial microbes help the plants grow better in the cold? Would they protect the plants from attackers? The scientists waited to see.
The practice of looking to extreme environments for new, exciting compounds or drugs falls under what's called bioprospecting. And, indeed, from hot springs to acid lakes, the extreme environments of the Earth have been a rich source of useful compounds.
The most notable would probably be a compound called Taq DNA polymerase, a compound that is used in a huge swath of modern biological science, and which was found in a heat-loving strain of bacteria able to survive in Yellowstone geysers.
But glaciers have also proven to be a rich source of compounds. Because of the extreme cold and other quirks of glacial life, enzymes from glacial microbes may come with novel abilities, like continuing to work even at low temperatures where normal enzymes would stop. Or they could be easily deactivated by even mild heat, giving chemists an easy off-switch to a chemical reaction.
Previously discovered compounds from glaciers or other chilly environments have already shown up in washing machine detergents, bread baking ingredients, ice creams and cosmetics. They have also been used in more esoteric products that the average consumer may never see or recognize, but which offer biotech researchers the ability to tweak a molecule just so. This ability could conceivably play a critical role in the next vaccine or medicine.
And there may be a wealth of new compounds and applications waiting to be discovered or perfected.
Back in the lab, Yarzábal's team let the wheat seeds grow for 16 days before digging them up. Judging by the length of the seedling's roots and shoots, they found that the wheat seedlings that'd been treated with the glacial bacteria did, indeed, seem healthier than their peers. Even the seedlings that'd been exposed to disease fared better. When the team investigated further, it appeared that the bacteria may have made it easier for the plants to take in phosphorus, a necessary nutrient, while some compound produced by the bacteria drove off the pathogens. It was evidence that microbes isolated from glaciers may, indeed, be able to help plants grow.
A vanishing resource
Unfortunately, the samples that led to this discovery may be some of the last to ever be collected from Venezuelan glaciers. As climate change has continued, the glaciers in Venezuela have all but disappeared. One of the final two glaciers is now completely gone. The other, La Corona, is down to about one-twentieth of a square kilometer, based on 2019 readings -- about a fourth of what it was in 2009. Shaded from the sun by a rock outcrop, that tiny patch is all that's left of Mérida's glaciers.
Venezuela isn't the only country on the verge of losing its ice fields. Tropical and mountain glaciers elsewhere, like those in Indonesia, are also disappearing. And while thick glaciers do still exist -- indeed, Greenland and Antarctica are still covered in thick ice sheets -- the overall picture is grim. A paper in the journal Nature from April 2021 found that nearly all glaciers are losing mass and losing mass faster than before.
"We have already made a real gap in the total glacier ice on earth," said Richard Alley, a geologist at Penn State and expert on global glaciers.
Ironically, the microbes that depend on the glaciers may be playing a role in their demise.
Aarhus University's Anesio said that he's preparing for an upcoming trip to Greenland, where he and his team will be camped out high on the inland ice sheets to study this possibility. The first members of the team and their supplies have already made the trip, first via boat to the coastal town of Qaqortoq, then via helicopter up to the ice.
On the glacier, Anesio will be trying to understand the surface microbes and how they grow. Satellite imagery has shown that the Greenland ice sheet is getting darker. Dark colors absorb more of the sun's energy than light ones, which could heat up the glacier and make it melt faster. And the microbes, which use pigments to absorb the sun's energy, are darker than the surrounding ice. So, does that mean the glacial algae may actually speed up glacial melt? Understanding how they grow, what holds them back, and what may be changing could help answer this question.
Unfortunately, for those working in Venezuela, climate change hasn't been the only problem.
Over the past few decades, the country has been rocked by political, economic and humanitarian crises. In 2014, spurred by high rates of violence and homicide in the country, Yarzábal and his family accepted an invitation to move from Venezuela to Ecuador.
Since then, more than 5 million people have fled Venezuela's violence, political instability and hyperinflation.
This crisis has also had an impact on science, shuttering the country's educational and research operations. Some of Yarzábal's glacier-going colleagues have remained at the University of the Andes in Mérida, but with few resources, their ability to study the final days of Venezuela's glaciers has been limited.
The samples Yarzábal collected back on that hike in 2012 are still preserved in an ultracold freezer, but Yarzábal is worried electricity shortages could put them in real danger of being thawed and lost forever.
"This is an example of how science can be really impacted by political measures," said Yarzábal. "We will not have a second chance. The glaciers have already disappeared."