Giant viruses on Greenland’s ice could help reduce melting

The algae blackens the ice. When that happens the ice reflects less sunlight and melts faster. Several areas in Greenland are covered with black algae. Credit: Laura Perini.

Every spring, when the sun returns to the Arctic after months of darkness, life comes back in full force.

Polar bears emerge from their dens, Arctic terns fly back from their southern journey, and musk oxen move north.

But these animals aren’t the only ones waking up with the sun. Algae that have been dormant on the ice start to bloom, turning large areas of the ice black.

When the ice turns black, it absorbs more sunlight instead of reflecting it, which speeds up the melting process.

This accelerated melting contributes to global warming. However, researchers might have found a natural way to control the growth of these algae and potentially slow down the 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.

Their findings, published in the journal Microbiome, suggest that these viruses might feed on the snow algae and could act as a natural control mechanism for the algae blooms.

“We don’t know much about these viruses yet, but they could help reduce ice melting caused by the algae. We still need to determine how specific and efficient they are, but further research might provide those answers,” says Perini.

Viruses are usually much smaller than bacteria. Regular viruses measure between 20 and 200 nanometers, while a typical bacterium is about 2-3 micrometers, making viruses about 1,000 times smaller than bacteria.

However, giant viruses are different. They can grow up to 2.5 micrometers, which is larger than most bacteria.

Additionally, giant viruses have a much larger genome. While bacteriophages (viruses that infect bacteria) have genomes with 100,000 to 200,000 letters, giant viruses have around 2.5 million letters.

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. But this is the first time giant viruses have been found living on the surface ice and snow dominated by microalgae.

“We analyzed samples from dark ice, red snow, and melting holes (cryoconite). In both the dark ice and red snow, we found signs of active giant viruses. This is the first time they’ve been found on surface ice and snow containing a high amount of pigmented microalgae,” Perini explains.

This discovery opens up new possibilities for controlling algae growth on ice and potentially slowing down ice melt. While more research is needed to understand these giant viruses fully, they could play a crucial role in reducing the impact of algal blooms on ice melt and global warming.