Researchers may have found a way to control the algae growth and potentially reduce ice melting. Postdoc Laura Perini from the Department of Environmental Science at Aarhus University and her team have discovered giant viruses living on the ice alongside the algae. Perini suspects that these viruses feed on the snow algae, potentially serving as a natural control mechanism.
"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," she says.
First discovery on ice
Giant viruses were first discovered in 1981 in the ocean, where they specialized in infecting green algae. Later, they were found in soil and even in humans. However, this is the first time giant viruses have been found on surface ice and snow dominated by microalgae, Perini explains.
"We analyzed samples from dark ice, red snow, and melting holes (cryoconite). In both the dark ice and red snow we found signatures of active giant viruses. And that is the first time they've been found on surface ice and snow containing a high abundance of pigmented microalgae."
Previously thought to be barren, this part of the world is now known to host several microorganisms, including giant viruses. Perini notes, "There's a whole ecosystem surrounding the algae. 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."
Microscopic discovery
Despite being classified as giant, these viruses cannot be seen with the naked eye or even with a light microscope. Perini discovered them by analyzing the DNA in samples taken from the ice. By identifying specific marker genes, she found sequences similar to known giant viruses.
To confirm the viral DNA came from living and active viruses, they extracted all the mRNA from the sample. The presence of these sequences indicated the viruses are alive and active on the ice.
"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," she says.
Uncertain functionality
Little is known about giant viruses due to their recent discovery. Unlike most viruses, they have many active genes allowing them to repair, replicate, transcribe, and translate DNA. The exact reasons for these capabilities and their specific hosts remain unclear.
"Which hosts the giant viruses infect, we can't link exactly. Some of them may be infecting protists while others attack the snow algae. We simply can't be sure yet," says Perini.
Her research is ongoing, with more findings expected soon. "We keep studying the giant viruses to learn more about their interactions and what is exactly is their role in the ecosystem. Later this year we'll release another scientific with some more info on giant viruses infecting a cultivated microalgae thriving on the surface ice of the Greenland Ice Sheet," she concludes.
Research Report:Giant viral signatures on the Greenland ice sheet
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Department of Environmental Science at Aarhus University
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