Why is Lake Hillier pink?
Meet the salt-loving cells responsible for painting Lake Hillier its lurid colour
On an island off the coast of Western Australia, you might expect the abundant sunshine to highlight a feast of colour for your eyes. However, the turquoise of the shallow waves and sun-kissed greens in the trees of Middle Island are interrupted by a contrasting body of intense pink. Though an irregular shade to grace any of Earth’s natural landscapes, this is no trick of the eye. This is Lake Hillier, an entirely pink lake.
After its discovery in 1802 by a Royal Navy explorer, it was soon realised that this lake was as rich in salt as it was colour. The lake has a salt concentration around ten-times higher than the ocean that surrounds the island. This made it a prime target for salt miners, who extracted the mineral from it for years. Today, however, the natural wonder is protected, and the lake serves mainly as a tourist attraction. Onlookers gaze in awe at the delightfully pink tones, bordered by its dry-salt shore, with many asking how it is possible for a lake to be so pink.
As much as the lake resembles a human-made pool of strawberry milkshake, the answer to this question comes only from nature. Lake Hillier is thought to gain its colour mainly from a microorganism called Dunaliella salina. This algae has adapted to thrive in the lake’s extremely salty conditions using a pink pigment to survive the high salt concentrations that are toxic to other organisms.
There are no fish or other wildlife to be seen in the peculiar pink waters, but what it lacks in fish it makes up for in microorganisms. Being one of the few species able to thrive in this lake, the huge population of Dunaliella salina algae is reflected in the colour. They produce carotenoid pigments called beta-Carotene, and it is this that scientists believe produces the vibrant pink.
Other microorganisms found in the lake which contribute to the pink hue are the halophilic archaea Halobacterium salinarum residing within the salt crusts. The term halophilic means ‘salt-loving’, which all organisms in Lake Hillier have to be to stand a chance of living in those conditions. With tough cell walls, these are capable of living in some of the world’s most extreme environments – and they also happen to be pink.
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