Lake Hillier is one of Australia’s most famous pink lakes, featuring widely across social media and in the media. It’s located off the coast of Esperance in Western Australia on Middle Island, the largest of the islands that make up the Recherche Archipelago.
It was discovered in 1802 by a British explorer called Matthew Flinders, who spotted the pink hue when he climbed the highest peak on the island.
No one really knows EXACTLY what causes the bright, bubblegum pink colouring of Lake Hillier, but a team of researchers from the eXtreme Microbiome Project (XMP) have identified a few probable suspects.
Australian Geographic recently published this article:
In 2015, Ken McGrath, a researcher for the XMP, collected genetic information from Lake Hillier sediment and water samples. Not many organisms can survive on lake beds made of solid salt, but extremophiles like the ones found in Lake Hillier thrive in this environment. The goal of the research was to identify the various extremophiles living in the lake that could be responsible for its remarkable colour.
Analysis of the material showed around 10 species of salt-loving bacteria, archaea and several species of Dunaliella algae. Nearly all these organisms are pink, red or salmon-coloured, and are the probable culprits of the lake’s strange colour. Most surprisingly, 33 per cent of the millions of DNA sequencing reads that the team generated from the lake water samples matched a single species of bacterium, called Salinibacter ruber.
“The most abundant DNA that we recovered from the lake came from a bacterium called Salinibacter ruber, a salt-loving halophile which also produces red pigments,” said Ken McGrath.
For a long time, it was assumed that micro algae was responsible for Lake Hillier’s pink colour. The findings from XMP, however, reveal the pink colour most probably arises from a bacterium. “Dunaliella alga is present but it’s not the dominant organism by any means,” said Ken. “Our genetic sequencing confirms that it is the bacterium that is the real reason the lake is pink.”
The dominant bacterium produces a pigment, called bacterioruberin, which helps the organism harvest light for energy. Unlike the pigments produced by algae, which are confined to the chloroplasts, bacterioruberin is spread across the entire bacterial cell. This means, when you look at the lake, you mostly see the pink colour of the bacteria.
So there you have it! A very scientific answer to a commonly asked question.
TOP TIP: There is a Pink Lake located in Esperance township, however, despite its name, this is no longer pink. The bright pink lake pictured above is out on Middle Island.
If you want to see Lake Hillier for yourself, you can take a scenic flight with local operators, Goldfields Air Services, or once a year Esperance Island Crusies also run a full day boat trip out to the island.