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Off the coast of Western Australia, a remarkable body of water captivates observers with its astonishing, vivid hue. This natural wonder, Lake Hillier, maintains a distinct, permanent coloration, unlike many other pink lakes around the globe that may experience temporary shifts. Nestled on Middle Island, the largest island of the Recherche Archipelago, its unusual appearance is a testament to the fascinating interplay of biology and extreme environmental conditions.
The striking color of Lake Hillier is primarily attributed to a unique ecosystem of microorganisms thriving within its highly saline waters. Scientists have identified the microalgae Dunaliella salina as a key contributor. This salt-loving organism produces carotenoids, red-orange pigments similar to those found in carrots, as a protective mechanism against the intense sunlight and extreme salt concentrations. Additionally, halophilic bacteria, such as Salinibacter ruber and various archaea, residing in the lake's salt crusts further enhance its vibrant coloration. The lake's salinity is significantly higher than that of the adjacent ocean, creating an ideal habitat for these extremophiles to flourish and produce their distinctive pigments.
The existence of this extraordinary lake was first documented in 1802 by British navigator and cartographer Matthew Flinders. Upon ascending the island's highest peak, now known as Flinders Peak, he observed "a small lake of a rose colour" and noted its high salt content. Flinders later named the lake in memory of William Hillier, a crew member of HMS Investigator. Lake Hillier is surrounded by a rim of sand and dense eucalyptus and paperbark trees, with a narrow strip of vegetated sand dunes separating it from the deep blue Southern Ocean, creating a breathtaking visual contrast (Review) that highlights its unique, permanent pink. While salt was briefly extracted from the lake in the early 20th century, it is now preserved as part of the Recherche Archipelago Nature Reserve, a protected area.