Earlier this month, Antarctica experienced record high temperatures, causing the southernmost continent’s ice caps to melt at an unprecedented rate. As a result, Eagle Island, a small island off Antarctica’s northwest tip, experienced peak melt; brown rock appeared from beneath the ice and several ponds of melt water accumulated at the center.

And with these unprecedented temperatures, the algae that normally thrive in freezing water and lie dormant across the continent’s snow and ice are now in full bloom and cover the Antarctic Peninsula with blood-red, flower-like spores.

On February 24, the Ministry of Education and Science of Ukraine posted photos of the phenomenon to their Facebook page, showing ice around their Vernadsky Research Base—located on the Galindez Island off the coast of Antarctica’s northern Peninsula—covered in what researchers call “raspberry snow” or “watermelon snow”. This red-pigmented algae, also known as Chlamydomonas nivalis, has the potential to jumpstart a feedback loop of warming and melting, worrying scientists about the continued impact of climate change on this critical region.

“Snow blooms contribute to climate change,” the Ministry wrote on Facebook. “Because of the red-crimson color, the snow reflects less sunlight and melts faster. As a consequence, it produces more and more bright algae.”

“Blood red” snow has been observed many times before. Aristotle noticed this phenomenon in the third century B.C., reports Brandon Specktor of Live Science. In 1818, Captain John Ross found pink snow during his expedition through the Northwest Passage; though he first thought it was iron-nickel meteorite.

Chlamydomonas nivalis is actually more widespread than people might think. The species is the most common type of snow algae found in snowfields and mountains across the world, reports Jennifer Frazer at Scientific American.

But this type of algae is actually a member of the green algae family. It won’t turn red until the weather warms up, the cell’s carotenoids—the same pigment that gives pumpkins and carrots their orange hue—absorb heat and protect the algae from ultraviolet light, almost like sunscreen, reports Aristos Georgiou of Newsweek. The more sunlight the algae receive, the more it produces the “watermelon red” pigment, which causes the snow to melt faster. And according to Ukrainian researchers, this phenomenon makes it easy for the species to enter a feedback loop of warming, melting and blooming, Live Science reports.

As the climate and its ecosystems continue to change due to human intervention, other extreme algal blooms have appeared in oceans around the world. In Spain’s Tossa de Mar, for example, sea foam invaded the coastal town’s beaches after a large storm brought strong winds and waves. Along the coast of the East China Sea and Taiwan’s Matsu Islands, toxic bioluminescent algae called dinoflagellates light up the ocean surface with a bright blue glow. And a rust-colored kind of alga, Karenia brevis, blooms along the Florida coast and releases a toxin that targets fishes’ central nervous system.