Why This Australian Lake Is Bubblegum Pink

Fly over Middle Island off the south coast of Western Australia and you will spot something that looks almost fake: a lake the color of bubblegum, sitting just a few hundred meters from the deep blue of the Southern Ocean.

A Lake Like No Other

Lake Hillier is a small saltwater lake on Middle Island, part of the Recherche Archipelago, a cluster of islands off Esperance in Western Australia. It measures roughly 600 meters long and 250 meters wide, ringed by a thin band of sand and a wall of eucalyptus forest. British explorer Matthew Flinders climbed a nearby peak and spotted the lake in January 1802, recording its odd rose color in his ship's log.

Why Is It Pink?

For years, the color was blamed on a microscopic algae called Dunaliella salina, which produces a reddish pigment when stressed by high salt levels. A 2015 DNA-sequencing study by molecular biologist Ken McGrath complicated that story. The algae made up only about 0.1 percent of the genetic material sampled from the lake. A salt-loving bacteria called Salinibacter ruber made up 20 to 33 percent instead, living in thick crusts of salt around the shoreline. Researchers now think the color comes from a mix of pigmented microbes crowding the hypersaline water and crust, not one single organism.

It Stays Pink Even in a Jar

Unlike some other pink lakes around the world, which fade in and out of color as temperatures rise and fall with the seasons, Lake Hillier historically held its shade no matter the weather. Scoop a sample into a sealed bottle and, unlike many natural dyes, it does not fade back to clear. For roughly two centuries after Flinders logged it, visitors and scientists reported the same vivid pink, rain or shine.

Is It Safe to Swim In?

Yes. Despite salt levels comparable to the Dead Sea, swimming in Lake Hillier carries no known health risk. Drinking the water is a different matter. The extreme salinity, along with the microorganisms living in it, makes it unsafe to consume.

A Recent Change

That two-century streak broke in 2022. Unusually heavy rainfall dumped large amounts of fresh water into the lake, diluting the salt levels its pink microbes depend on. The lake turned a dull blue-gray, and by some recent reports it has not fully returned to its old hue. Scientists studying the site expect salt levels to climb again as the excess water evaporates, and predict the pink could fully return within five to ten years.

For now, Middle Island's strangest resident is doing what it has always done best: waiting for the salt to build back up, and the color to come home.