The Colors Of Climate Change: The Pink Lake Phenomenon

Late last year, U.S. Fish and Wildlife Service staff at Keālia Pond National Wildlife Refuge were called to the scene to check out what some believed to be a toxic algal bloom—the water had turned bright pink. A coastal salt marsh on Maui that’s home to a wide variety of waterbirds, the pink-tinged wetland looked like something out of a fairytale. 

While this was the first known instance of pink waters in Hawaii, this phenomenon—which scientists discovered wasn’t caused by toxic algae—is common in many places. In fact, climate change may cause pinker waters across the world.

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The Science Of Pink Lakes

Bubblegum pink lakes are dotted across Western and South Australia—Lake Hillier, Hutt Lagoon, Lake Bumbunga and Lake MacDonnell being some of the most popular with travel Instagrammers—and can also be found in Senegal, Spain, and the Caribbean.

Contrary to what one might expect, the striking pink coloration of these lakes is not the result of artificial dyes or chemical pollutants—rather, it’s an interplay of environmental factors. The primary agents responsible for this phenomenon are algal and bacterial microorganisms that thrive in high-salinity environments. 

These extra-salty pink bodies of water aren’t as rare as you might think, and they aren’t always pink. In fact, Keālia Pond National Wildlife Refuge isn’t the first pink lake in the U.S.—the Great Salt Lake’s North Arm in Utah, which was cut off from freshwater with the construction of a railroad in the 1950s, nearly doubled its salinity, turning its waters a dusky rose color. 

Much to the dismay of travel influencers, other pink lakes vary greatly in hues depending on weather patterns and climate trends. 

Central to the formation of pink lakes are high concentrations of salt in the water. As water evaporates from the surface of these lakes, the remaining water becomes increasingly saline, creating an environment conducive to the growth of tiny organisms that produce pigments that act as a protective mechanism against the harsh conditions of their habitat. When conditions are just right—specifically, when the water becomes sufficiently saline and the sunlight is intense enough—the proliferation of these pigmented microorganisms gives rise to the characteristic pink hue that defines these lakes.

This process is furthered in arid regions with limited rainfall, where evaporation rates outpace replenishment, leading to the accumulation of salt and greater intensification of the pink coloration.

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Shifting Shades Of Climate Change

The delicate organic chemical balance that causes the existence of pink lakes may be at risk in the face of climate change. As global temperatures rise and weather patterns become increasingly erratic, the precarious microbiomes of pink lakes are vulnerable to disruption. Changes in precipitation patterns and evaporation rates could alter the salinity levels of these lakes, potentially affecting the abundance and distribution of microorganisms. In turn, this could lead to greater shifts in the intensity and duration of the pink coloration, with greater implications for these dynamic ecosystems.

Keālia Pond’s pink water certainly seems connected to drought. As of December, much of Maui was under abnormally dry to severe drought conditions. Typically, the Waikapu Stream flows into the pond, raising water levels and reducing salinity, but its flow has been disrupted, reducing freshwater input and causing the salinity of the Keālia Pond outlet to spike to more than 70 parts per thousand—twice that of seawater. 

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Preserving The Pink

Beyond their striking aesthetic appeal, pink lakes play a crucial role in local ecosystems, serving as vital habitats for a diverse array of organisms. Due to the high salt content of established pink lakes, the waters are typically only home to microorganisms and migratory birds.

These Barbie-pink waters are more than just a photogenic tourist destination—they may also be a sign of warming temperatures and drier conditions driven by climate change. The combination of the two factors could make waters even saltier. In Western Australia, scientists are anticipating seeing even more expanses of Pepto Bismol-colored water in coming years. 

While some bodies of water may start turning pink, it’s also possible that climate change-fueled drought could cause others to dry up entirely. It’s been hypothesized that climate change may have the entirely opposite effect—depending on the location and hydrology of a pink lake, lakes in areas experiencing heavier rainfall might lose their bubblegum hue entirely. The formerly-famous Pink Lake in Esperance, Western Australia, has been a milky white color for several years.

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Evolving Hues Of Pink Lakes

Is it possible to appreciate the phenomenon of the pink lakes without reflecting on the human activities that may have exacerbated these conditions? Scientists think that the answer is nuanced. On one hand, the chemistry behind pink lakes has existed far before climate change—the bodies of water in Australia in particular had significant cultural meaning for Aboriginal and Noongar people.

On the other hand, it’s hard to decipher decisive climate action from a phenomenon that’s caused by years-long climate patterns. Perhaps the answer is as simple as this—from the microbial communities that paint our waterways pink to the global forces shaping their fate, pink lakes serve as a reminder of the interconnectedness between human activities and the natural world.