In the Arctic, where life seems to disappear during the long, dark winter months, spring brings a reawakening. Polar bears emerge from their winter lairs, arctic terns return from their southern sojourns, and musk oxen trudge northward. But it’s not just the animals that spring back to life; algae lying dormant on the ice also begins to bloom, turning large swaths of the ice black.
This darkening of the ice reduces its ability to reflect sunlight, accelerating the melting process and exacerbating global warming. However, researchers may have found a way to control the growth of snow algae and potentially reduce some of the ice melt. Postdoc Laura Perini from the Department of Environmental Science at Aarhus University and her colleagues have discovered giant viruses living alongside the algae on the ice.
A First: Giant Viruses Found on Surface Ice and Snow
Giant viruses, first discovered in the ocean in 1981, have been found in various environments, including soil and even humans. But this is the first time they’ve been found living on the surface ice and snow dominated by microalgae. Laura Perini and her team analyzed samples from dark ice, red snow, and melting holes (cryoconite) and found signatures of active giant viruses in both the dark ice and red snow.
“There’s a whole ecosystem surrounding the algae,” Perini explains. “Besides bacteria, filamentous fungi and yeasts, there are protists eating the algae, different species of fungi parasitizing them and the giant viruses that we found, infecting them. In order to understand the biological controls acting on the algal blooms, we need to study these last three groups.”
Unraveling the Mysteries of Giant Viruses
Despite their name, giant viruses can’t be seen with the naked eye. Perini and her team discovered the viruses by analyzing all the DNA in their samples and looking for specific marker genes that have high similarity to known giant viruses. To ensure that the viral DNA came from living and active viruses, they also extracted all the mRNA from the samples.
“In the total mRNA sequenced from the samples, we found the same markers as in the total DNA, so we know they have been transcribed. It means that the viruses are living and active on the ice,” Perini says.
However, much remains unknown about giant viruses, including which hosts they infect and what they use their active genes for. Perini suspects that the viruses feed on the snow algae and could work as a natural control mechanism on the algae blooms, but more research is needed to confirm this.
“We don’t know a lot about the viruses, but I think they could be useful as a way of alleviating ice melting caused by algal blooms. How specific they are and how efficient it would be, we do not know yet. But by exploring them further, we hope to answer some of those questions,” Perini says.
As researchers continue to study these giant viruses and their interactions within the Arctic ecosystem, they hope to unravel more of their mysteries and potentially harness their power to mitigate the effects of climate change on the delicate balance of life in the far north.
