Hidden on the remote fringes of Middle Island, the largest island in the Recherche Archipelago, lies one of the most visually surreal natural wonders on Earth: Lake Hillier. Unlike other pink lakes that fade, darken, or change colour with the seasons, Hillier remains an unshakable, almost fluorescent bubblegum pink — a colour so intense and so steady that it has baffled explorers, naturalists, and researchers for over two centuries.

From above, Hillier looks like a perfectly carved oval jewel of neon strawberry milk, resting between blinding white salt flats and dark, rugged eucalyptus forest. The contrast is so sharp that some early pilots believed the lake had been artificially dyed. But Hillier is 100% natural — a biological and chemical masterpiece formed by microbes, minerals, isolation, and harsh environmental stress.

To this day, the lake is considered one of the most stable and persistent pink lakes in the world, refusing to fade even when water is removed and placed in a container. Its distinct personality and uniquely consistent hue make it one of the planet’s greatest natural colour mysteries.

What follows is the most detailed, expanded scientific explanation of why Lake Hillier remains so pink — and why it is so different from every other pink lake on Earth.

The Microorganisms That Paint the Lake Pink

Dunaliella salina: The Extremophile Algae Behind the Colour

The star of Hillier’s pigment show is a tiny yet extraordinary alga called Dunaliella salina, a halophilic (salt-loving) microorganism capable of surviving in environments that would dehydrate or destroy most other life forms.

Dunaliella thrives in hypersaline waters where salt concentrations climb to extremes. In Lake Hillier, conditions are so hostile that very few species can compete — allowing Dunaliella to dominate the ecosystem.

Why Dunaliella Turns Pink

Under intense environmental stress, the alga produces an abundance of carotenoid pigments such as:

• Beta-carotene

• Zeaxanthin

• Lutein

• Other protective carotenoids

These pigments act as biological sunscreens, protecting the algae from:

• Lethal UV radiation

• Osmotic stress caused by salt

• Oxidative damage triggered by extreme conditions

In more typical environments, Dunaliella remains green, but in Hillier, the unrelenting combination of salt and sunlight forces the organism to overproduce pigments — giving the water its warm orange-pink glow.

The Algae Are Suspended Throughout the Water

Unlike some lakes where pigment settles, Dunaliella floats freely throughout Hillier, tinting:

• The surface

• The mid-depth water

• Even deeper zones

This creates the lake’s smooth, uniform, “painted” appearance.

Halobacteria: The Pink-Tinted Salt-Lovers

The story doesn’t end with algae. Hillier is also home to halophilic archaea — microorganisms that actually love extremely salty environments and would die in normal freshwater or seawater.

Key species include:

• Halobacterium

• Halococcus

• Haloferax

These archaea contain bacterioruberins, strong red pigments that protect them from the same intense UV radiation that bombards Dunaliella.

How Halobacteria Deepen the Colour

Unlike algae, these archaea accumulate:

• In salt crusts

• In brine pockets

• On sediment layers

• In tiny clusters throughout the water column

Their magenta, ruby, or deep pink tones blend with Dunaliella’s orange-pink pigments, creating a multi-layered colour spectrum that transforms the lake into a giant natural “biochemical canvas.”

This microbial partnership is one of the rarest and most stable pigment ecosystems in the world.

Extreme Salinity: The Lake’s Secret Engine

Lake Hillier’s salinity is extraordinarily high — often rivaling or exceeding the Dead Sea. This hyper-salt environment is not just a background condition; it is the engine that drives the lake’s unique colouration.

Why High Salinity Matters

1. It forces Dunaliella to produce carotenoids.
   No salt → no stress → no pigments → no pink.

2. It kills off almost all competing organisms.
   Meaning the pigment-producers dominate the environment.

3. It preserves pigments.
   Salt acts as a natural preservative, preventing the breakdown of delicate biological compounds.

4. It stabilizes the ecosystem.
   With few species able to survive here, the lake becomes a near-closed microbial community.

This stability is a major reason Hillier’s colour is so consistent year after year.

Sunlight, Heat, and Evaporation Amplify the Colour

Lake Hillier is shallow, warms up quickly, and is exposed to intense Western Australian sunlight. This creates an ideal “stress chamber” for pigment production.

Dry and Hot Periods → Stronger Pink

• Higher evaporation

• Increased salt concentration

• Triggered stress response in algae

• More carotenoids produced

• Water becomes deeper pink

Wet or Cooler Periods → Slightly Softer Pink

• Lower salinity

• Reduced stress

• Less pigment created

But unlike many pink lakes, Hillier never loses its colour completely.

This resilience is extremely rare and is one reason scientists consider Hillier a microbiological treasure.

The White Salt Crust Enhances the Colour

Lake Hillier is bordered by glittering white salt formations. These bright edges reflect sunlight directly into the shallow water, amplifying the natural pigments.

The effect is similar to:

• Turning up the brightness on a screen

• Placing a pink object on a white background

• Increasing colour contrast in a photograph

This helps explain why Hillier appears especially vibrant when seen from the air.

The Water Stays Pink Even Outside the Lake

One of Lake Hillier’s most unusual features is that its water remains pink even after being removed from the lake and stored in a container.

This proves:

• The colour is not a trick of light

• The colour does not depend on minerals in the lake bed

• The pigments are literally suspended in the water itself

• The microorganisms continue to “dye” the water wherever they go

This is scientifically important because many pink lakes lose their colour immediately once water is removed — making Hillier a microbiological anomaly.

A Rare Biological and Geological Combination

To create a pink lake like Hillier, nature needs a precise combination of conditions — and Hillier has every one of them:

• Isolation from external water sources

• An enclosed, stable basin

• Extremely high salinity

• Strong UV exposure

• The presence of Dunaliella salina

• A thriving halobacteria population

• A climate that reinforces evaporation

• A lack of competing species

• Minimal human disturbance

This is an exceedingly rare recipe. Globally, fewer than 20 true pink lakes exist — and none behave quite like Hillier.

A Brief History of Exploration and Curiosity

Lake Hillier was first recorded in 1802 by the British navigator Matthew Flinders, who climbed a nearby peak and was stunned by the lake’s unusual colour. His journals describe it as “a lake of rose-coloured water,” a discovery so unexpected that early naturalists believed it might be a mineral reaction.

In the early 1900s, the lake was briefly used for salt harvesting, but the project failed due to:

• The island’s remoteness

• Harsh weather

• Difficult access

• Limited freshwater sources

Today, Hillier is protected as part of the Recherche Archipelago Nature Reserve, and only small-scale scientific expeditions are allowed.

The only way to view the lake now is by scenic flight, making it one of the least disturbed pink lakes on Earth.

What Makes Lake Hillier So Different From Other Pink Lakes

While Australia is famous for its pink lakes — including Hutt Lagoon, Lake Bumbunga, Lake MacDonnell, and Lake Hart — Lake Hillier stands apart.

Hillier’s Pink is:

• Permanent (does not fade seasonally)

• Bubblegum-coloured, not salmon or red

• Intensely uniform due to suspended algae

• Unaffected by rainfall compared to many lakes

• Amplified by its bright white salt rim

• Surrounded by dense forest, giving a dramatic contrast

This combination gives Hillier a uniquely photogenic, almost “painted” appearance unmatched by any other lake.