Posted on January 22 2019
There are some lakes, like Tahoe, that can be crystal clear. Even those rare bodies are increasingly plagued by incursions of pollution or sediment that mar the clarity to some extent. And most lakes don’t come close to that kind of visibility, especially in summer when warmer water is so conducive to the growth of algae. Green, then, is a pretty common hue for lake waters, along with those blues, and some that are brown thanks to high iron content. There is yet another color that is part of the lake palette, and it’s not the kind of earth tone you might expect. In fact, it’s one that looks more natural on bubble gum or a Mary Kay Cadillac—pink!
In a number of places around the world, conditions are such that lake water takes on what would seem to be a wildly unnatural pink color. It won’t happen in a lake you might think to dip a cup into for a drink of water. OK, that‘s probably not a smart idea in any lake, given the impurities present in most, but the reason pink lakes are so unpotable is that they are hypersaline. It’s this high concentration of salt that makes the waters inhospitable to most life forms, and so inviting to archaea. Archaea are ancient microbes, some forms of which tend to go for environments that are out of the question for other kinds of life. Their members can be found in boiling hot deep-ocean rift zone vents and in steaming hot springs at the surface in places like Yellowstone. The archaea in pink lakes are highly salt-tolerant, and produce carotenoids, pigments such as the red-orange beta carotene. When concentrations are high enough, the color effect is quite striking. If lake waters become more dilute, the lower salinity can lead to mellower shades of pink, or none at all. Some of these organisms are so hardy that they can hibernate in salt crystals for years, waiting for environmental conditions to become more supportive. In addition to the archaea, a salt-tolerant green alga called Dunaliella salina also contributes to the pinkness, though not as strongly.
Pink lakes are great for tourism—who wouldn’t want to post a selfie with pink water in the background? They also draw another group of tall, two-legged creatures: flamingoes. In fact, the famously pink flamingoes owe their color to the beta carotenes in the brine shrimp, algae, and archaeans they feast upon. At birth, flamingoes are a dull gray and only develop as much pinkness as their natural diet provides. Flamingoes living in zoos have to be fed synthetic supplements to keep them, uh, in the pink. Besides tourism and bird habitat, in some locations pink lakes also support the economy as salt mines. Most of these internally draining lakes are not particularly broad or deep, which means evaporation can more quickly concentrate the salts in which the halophilic archaea thrive. The salinity of these lakes is several times that of sea water, so they can provide an abundance of salt. And not surprisingly, the harsh and unusual waters of pink lakes are seen by some as a tonic, and they claim that a good soak there leaves them feeling rejuvenated—and probably a little salt encrusted.
Pink lakes—what’s next, purple forests? Nature never fails to astound, and the effect is all the more intriguing when the facts behind the phenomenon are learned. Thanks for reading the Geo-Joint and being curious about our wild and crazy world.
Is bright pink Lake Hillier on your bucket list now? Get this Hema travel map of Australia to help you get closer to the lake’s home on tiny Middle Island off Western Australia. Maps.com can set you up!
caption: Lake Hillier, a pink lake on an island off southwestern Australia, has a setting of remarkable color contrast.
source: Wikimedia Commons: Kurioziteti123 (CC by SA 4.0 International)
caption: Lake Retba, not far from Dakar, Senegal is the site of small-scale salt production. Workers guard their skin from the harsh waters by applying shea butter, made from locally native shea tree nuts.
source: Wikimedia Commons: Anthea Spivey (CC by SA 4.0 International)
caption: Flamingoes turning themselves pink in Lake Amboseli, Kenya.
source: Flickr: Ray in Manila (CC by 2.0)
caption: A pink pond seen from space—Marharloo Lake by Shiraz, Iran.
source: Wikimedia Commons: Samantha Cristoforetti/NASA (Public domain)
caption: And those purple forests—nature provides those too!
source: Flickr: John (CC by SA 2.0)