Giant viruses discovered in Greenland could slow ice melt

Danish scientists have discovered giant viruses on the surface ice in Greenland.

These organisms are giant in relative terms – around 2.5 micrometres compared to 0.02-0.2 microns in typical viruses, and with genomes around 10 times longer. While ‘giant’ they’re still impossible to see without a microscope.

Viruses are long known as inhabitants of oceans, under Arctic permafrost and in larger organisms, but these were found beside mats of algae covering the ice sheets and were detected when algal samples were sequenced. This exposed lines of genetic code similar to other known viruses.

But the true nature of Greenland’s giant viruses isn’t known.

Laura Perini, an environmental microbiologist from Aarhus University in Denmark, thinks they may inject themselves into other organisms and effectively become a natural control for the spread of snow algae, when Greenland’s ice thaws in springtime.

“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,” Perini says.

“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.”

Rather than simply accepting the traces of viral DNA as evidence of the giant viruses’ existence, Perini hunted for signatures of short-lived messenger RNA – single-stranded genetic molecules used to encode for proteins in organisms.

RNA is short-lived in the environment, so evidence in the samples was used to confirm the presence of active viruses.

“We analysed samples from dark ice, red snow and melting holes [layers of microbial and mineral dust that covers glaciers],” Perini says.

“In both the dark ice and red snow we found signatures of active giant viruses. That is the first time they’ve been found on surface ice and snow containing a high abundance of pigmented microalgae.”

Those pigmented algae also pose an existential problem for Greenland. The massive ice sheet’s rate of melt is being exacerbated by global warming. But it has a defensive mechanism.

White snow and ice are reflective and a percentage of warming radiation from the Sun is bounced back towards space. But dark-coloured algae reduces Greenland’s albedo (a measurement of light reflectivity). Perini thinks giant viruses could be useful in controlling algal blooms on Greenland’s surface and stabilising albedo.

“I think they could be useful as a way of alleviating ice melting caused by algal blooms,” Perini says.

“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’s findings are published in the journal Microbiome.