Lake Hillier, in Australia has a ‘candy pink’ colour: What makes it look like that?

Nestled on Middle Island in the Recherche Archipelago off Western Australia, Lake Hillier looks like a scene from a fantasy painting, a candy-pink body of water ringed by white salt crusts and eucalyptus woodland. Its colour has fascinated sailors, scientists and tourists since Matthew Flinders first noted “a small lake of a rose colour” in 1802. What makes Hillier exceptional is not just its vivid hue but that the pink remains visible even when water is sampled in a bottle – indicating the colour comes from the water itself, not merely reflections or algae on the surface.

What gives Hillier its pink shade?

For decades the simple explanation pointed to the microalga Dunaliella salina, which accumulates orange-red carotenoids (notably β-carotene) under high salinity and intense light. But modern genetic studies have revealed a more complex microbial orchestra. Many pink lakes change shade with seasons; Hillier historically stood out because its pink colour often appears persistent in aerial photos and in-situ samples. Several local amplifiers help: the lake’s very high salinity, shallow depth, a reflective white salt rim, and limited mixing with open ocean waters concentrate pigment-bearing microbes and make the colour more visible. According to a 2022 research published by US National Institutes of Health, microbiome and metagenomic analysis of Lake Hillier, has shown pigment-rich microbes form a resilient community adapted to the lake’s unique chemistry – which helps explain the striking, long-standing hue.

A fragile balance and recent shifts

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Recent weather events have shown how sensitive that balance is. A major offshore rainfall/dilution event in 2022 reduced salinity and caused Hillier’s pink to fade in some observations; reporters and scientists noted colour loss in subsequent years, though many experts expect the pink to return as evaporation concentrates salts and pigment-producers rebound. These shifts highlight that the pink is not a permanent monument but an emergent property of hydrology, climate and microbial ecology.

Access, conservation and human interest

Lake Hillier sits inside a protected nature reserve; there are no public roads to Middle Island. Most people see the lake by scenic flight from Esperance, and on-land visits are tightly regulated to protect the fragile ecosystem and microbial communities that create the pink. While the salty water is not known to be acutely toxic, authorities discourage unrestricted landings or swimming to avoid ecological disturbance. Hillier’s photogenic nature also raises questions about tourism pressure and how to balance public interest with conservation.

Why this tiny pink lake matters

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Beyond its social media fame, Lake Hillier is a living laboratory for extremophile biology, microbial ecology and environmental sensitivity. Studying its microbes helps scientists understand how life adapts to high salinity and intense UV (ultraviolet radiation) – with lessons for biotechnology and even astrobiology. At the same time, Hillier reminds us that spectacular natural phenomena often depend on delicate environmental equilibria susceptible to climate variation and human influence. Protecting places like Middle Island means protecting both their beauty and the microbial worlds that produce it.