Although the intriguing fruit punch hues of Lake Koyashskoe might seem inviting at first glance, it's best not to take a sip. That's because this rosy, shallow body of water on the Crimean peninsula is chock full of salt — so much in fact that it lays claim to being the saltiest body of water in the country!
Of course, Lake Koyashskoe isn't alone in its briny grandeur. There are several scarlet-tinted salt lakes across the world — most notably Tanzania's Lake Natron, Australia's Lake Hillier and, of course, the northern half of Utah's Great Salt Lake.
So what makes these seemingly desolate lakes so vivid and colorful? Microbes! Specifically, single-celled organisms known as halobacteria. While most other life would be unable to stand living in such a harsh, salty environment, these tiny "extremophiles" thrive in high-salinity environments.
The rosy colors of halobacteria are produced by a pigmented protein known as bacteriorhodopsin, which is related to the rhodopsin protein that's used to sense light in the retinas of vertebrates. As phototrophic microorganisms, halobacteria use bacteriorhodopsin to absorb energy from the sun. To put it in its most simplistic terms, this process is very similar to the way plants use photosynthesis to absorb the sun's energy, except instead of using green-pigmented chlorophyll, halobacteria rely on the purple-pigmented bacteriorhodopsin.
What's particularly fascinating about Koyashkoe is that it comes and goes with the seasons, and the vibrancy of the lake's red hue is dependent on water levels. The less water there is, the more concentrated the colorful, salt-loving microbes are. This is best witnessed in the summer months, when the lake water gradually evaporates in response to the unrelenting heat. By the end of summer, the lake is almost entirely gone, and what's left behind is a glistening salt flat tinted with pink.