This lake's bubble-gum pink stays vivid in a jar—which one?

The Bubble-Gum Enigma on Middle Island

Lake Hillier sits on Middle Island in Western Australia's Recherche Archipelago, roughly 130 kilometers east of Esperance. The lake measures about 600 meters long, bordered by a rim of white salt crystals and surrounded by dense eucalyptus forest, with the Southern Ocean's turquoise waters visible just beyond a narrow strip of sand dunes. Discovered in 1802 by navigator Matthew Flinders during his circumnavigation of Australia, the lake drew immediate attention for its arresting color—a shade Flinders described in his journal as resembling a strawberry milkshake poured into the landscape. Unlike the continent's other saline lakes, which can shift from pink to white depending on seasonal algae blooms, Hillier maintains its bubblegum hue throughout the year, undimmed by winter or drought. The lake's color remains vivid even in aerial photographs taken at high altitude, making it a landmark for pilots navigating the southern coast.

The Microbial Cocktail Responsible

For decades scientists assumed Hillier's pink derived from Dunaliella salina, the same halophilic algae that tints Western Australia's Port Gregory pink and Senegal's Lake Retba a salmon shade. But water samples collected in the 2010s revealed a far more complex microbial ecosystem: the lake hosts at least ten species of salt-loving archaea and bacteria, including Halobacteria and Salinibacter ruber, which produce carotenoid pigments as a defense against intense ultraviolet radiation. These organisms thrive in Hillier's hypersaline environment—salt concentrations approach 340 grams per liter, nearly ten times that of seawater—and their combined pigments create the lake's signature color. Crucially, the pigments remain suspended in solution rather than settling out, so when researchers bottle the water and transport it to laboratories in Perth or beyond, the color persists. Genetic sequencing in 2016 identified additional extremophiles unique to Hillier, suggesting the lake functions as a isolated evolutionary laboratory where microbial communities have adapted in ways not seen elsewhere.

The Nineteenth-Century Salt Harvest That Failed

In the 1890s entrepreneurs arrived on Middle Island with plans to mine Hillier's thick salt crust for export to the Western Australian goldfields, where salt was essential for ore processing. Workers established a rough camp on the lakeshore and began scraping up crystallized salt, which formed in geometric plates along the water's edge. Within months the operation collapsed: Hillier's salt, though abundant, proved too contaminated with organic matter from the microbial blooms to meet industrial standards, and the remote location made shipping costs prohibitive. The abandoned equipment—rusted shovels, a collapsed timber jetty—remained on the island until the 1950s, slowly buried by drifting sand. Today the site is part of the Recherche Archipelago Nature Reserve, and access is tightly restricted to protect nesting colonies of shy albatrosses and Cape Barren geese that breed on Middle Island. The failed salt venture inadvertently preserved Hillier by making the lake economically worthless, ensuring it survived the century that saw many of Australia's smaller salt lakes drained or degraded.

Why the Color Still Matters

Lake Hillier has become a case study in astrobiology—the search for life in extreme environments beyond Earth. NASA researchers have compared Hillier's microbial ecosystem to conditions that may exist in the subsurface oceans of Jupiter's moon Europa and Saturn's Enceladus, where liquid water beneath ice shells might harbor similar halophilic organisms. The lake's pigments, stable across wide temperature and pressure ranges, offer clues to how extraterrestrial life might signal its presence through atmospheric or surface coloration. In 2018 Australian scientists isolated a strain of Salinibacter from Hillier that produces a carotenoid with potential pharmaceutical applications, including as an antioxidant and anti-inflammatory compound, though commercial development remains years away. Meanwhile, Hillier's fame has grown through social media and tourism campaigns, with scenic flights over the Recherche Archipelago now departing daily from Esperance, bringing thousands of visitors each year to glimpse the pink lake from the air—closer access remains prohibited to safeguard the fragile microbial balance that creates the color in the first place.