Giant viruses infect algae in one of the rarest floating lakes in the Arctic

(ORDO NEWS) — Giant viruses infecting microscopic algae have been found in a rare lake in the Arctic Ocean, a new study says.

Epishelf lake Miln Fjord is a body of fresh water located on top of sea water less than 500 miles (800 km) from the North Pole.

Researchers studying this lake found that the fresh water has a richer and more diverse spectrum of viruses than the salt water below it.

They also found “giant” viruses – several times larger than ordinary viruses – infecting microscopic algae just below the boundary between fresh and salt water.

“Just as the lake’s freshwater ecosystem is different from that of the Arctic Ocean, so is its virus community distinct,” study co-author Mary Thaler, a microbiologist at Laval University in Quebec.

An epishelf lake is held in place by ice but has no physical bottom. The fresh water of the lake floats above sea water because fresh water has a lower density than salt water.

The upper part of the lake is covered in ice, which protects the fresh water from waves and wind that would otherwise cause the two types of water to mix.

The researchers drilled through the ice and collected water samples from the lake. They then sequenced the DNA found in those samples to identify various viruses, including some belonging to a group of giant viruses called Megaviricetes.

“One of the things about viruses in general is how tiny they are, much smaller than the smallest bacterium, and only carry a few genes that help them replicate,” Thaler said.

“However, over the past 20 years, scientists have discovered giant bacteria-sized viruses with genomes that could potentially carry many interesting genes.”

Researchers don’t know how most viruses affect microscopic algae, or even which viruses infect which organisms, the American Society for Microbiology said in a statement.

The study authors hope to get more information about the ecosystem in the future, but they are in a race against time: rising temperatures threaten to destroy the ice dam that holds fresh water in place.

“Epishelf lakes used to be more common in the Arctic, but now they are extremely rare,” Thaler said. “If the ice dam collapses – which has already happened in other fjords – then the epishelf lake Miln Fjord will be lost.”


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