To the delight of Instagram aficionados around the world, Australia's bright pink lakes may be increasing in number, thanks to climate change.
The bubblegum-pink lakes found in the south of Western Australia draw vast numbers of tourists every year. They gain their strange hues from a collection of bacteria and algae living in the water. Because of the effects of climate change, new lakes may start turning pink, while others will dry out entirely.
These lakes, which are found dotted across Western Australia and South Australia, include Lake Hillier, Hutt Lagoon, Lake Bumbunga and Lake MacDonnell. The lakes are extremely salty and get their characteristic pink colors from the salt-tolerant algae that live in them. The main culprit is the green algae species Dunaliella salina, but other species of algae and bacteria have also been found in the lake waters and may contribute to the color.
Dunaliella salina can live in waters with up to a 35 percent NaCl (salt) concentration. By comparison, seawater contains only 3 percent NaCl. At very specific salinities, temperatures and light conditions, the algae may produce a red carotenoid pigment called beta-carotene—it gives carrots their red-orange hue—that may be responsible for the lake water turning pink.
"For climate change, halophilic (salt tolerating) bacteria are present in many of these locations, and can grow with the right conditions, including higher salinity and warmer waters," Gabriel Filippelli, a professor of Earth Sciences at Indiana University, told Newsweek.
"The pink pigment expressed by the bacteria in western Australia is beta-carotene and is produced by a number of halophilic bacteria. We see similar phenomena in other extreme lake environments, like in Yellowstone hydrothermal ponds," Filippelli says.
"Why these bacteria choose to express these proteins is still up for debate as there is a metabolic cost involved, but they must accord some ecological damage (perhaps inhibiting the activities of their competitors?)"
Climate change is expected to lead to lower levels of rainfall and higher temperatures across Australia's southwestern region. Therefore, these changing conditions are expected to alter the water content of the lakes, making some more salty and therefore more receptive to the color-changing algae.
"We are expecting that these lakes are going to receive less water and hold water for shorter periods of time," Angus Lawrie, a salt lake ecology specialist at Murdoch University, told radio station ABC Great Southern.
"Because pink lakes tend to be at the more saline end of salt lakes, we are probably expecting to see more pink lakes. It's only pink under the very specific circumstances that those microorganisms need to turn it pink," he said.
Some other lakes may dry out entirely, however.
"The climate change story can either increase the prevalence of a pink lake or it can reduce the prevalence of the permanent pink lakes that we have, whether it's Hutt Lagoon or Lake Hillier," environmental consultant Tilo Massenbauer told ABC Great Southern. "It all depends on the hydrology and where these lakes sit within the landscape, whether it's near the coast or inland."
Alternatively, increased rainfall driven by climate change may dilute the waters in a lake, making it less salty and, therefore, less ideal for the salt-loving algae.
"If a large rainfall event came down and sat on the Geraldton area, Hutt Lagoon would be impacted," Massenbauer said. "It's just depending on the lake's hydrology and how quickly we go straight back into a hot, dry period.
Beyond the colors of the lakes, Lawrie is concerned about the effects that changes to the lakes' salinity levels could have across the food web, especially migratory birds.
"If we see a decline in the habitat quality of salt lake environments, that will have really serious flow-on effects," he said. "[The lakes are] really important sources of food for a variety of wading bird species that might fly for thousands of kilometers to come and take advantage of these systems when they receive water."
The actual results of the changing climate on the lakes and their local ecology have yet to be seen, however, and may not be as bad as we fear, thanks to a species' ability to adapt, Lawrie said.
"In evolutionary terms, conditions in this part of the world have been much more severe in terms of aridity than they are right now," he said. "That's not to say that the rate of change that we are experiencing right now we have ever experienced before."
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Update 12/19/23, 1:59 p.m. ET: This article was updated with comment from Gabriel Filippelli.
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Jess Thomson is a Newsweek Science Reporter based in London UK. Her focus is reporting on science, technology and healthcare. ... Read more
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