Lake Hillier, located on Middle Island in Western Australia, presents a striking natural phenomenon with its vibrant pink waters. This unique body of water, approximately 600 meters long and 250 meters wide, offers a vivid contrast against the surrounding green eucalyptus and paperbark trees and the deep blue Southern Ocean. Its distinct bubblegum pink hue immediately captures attention. This article explains the science behind Lake Hillier’s unusual coloration.
The Microscopic Life Behind the Color
Lake Hillier’s distinctive pink color comes from specialized microorganisms. The microalga Dunaliella salina is a significant contributor to this vibrant hue. Under specific environmental conditions, this alga produces high concentrations of carotenoid pigments, like beta-carotene (also found in carrots). These pigments absorb light wavelengths other than red and orange, reflecting the pink to reddish spectrum.
Halophilic, or “salt-loving,” bacteria also contribute to the lake’s coloration. Species like Halobacterium salinarum and Salinibacter ruber thrive in its extremely salty environment. These bacteria produce reddish pigments, like bacterioruberin, intensifying the water’s pink and red tones. The combined effect of these microorganisms gives Lake Hillier its characteristic and consistent color.
How Extreme Salinity Fuels the Pink Hue
Lake Hillier’s extreme salinity creates an environment where only certain organisms can flourish. As a hypersaline lake, its salt concentrations are considerably higher than seawater, comparable to the Dead Sea. This high salinity acts as a selective force, making the lake inhospitable to most other aquatic life. Specialized microorganisms like Dunaliella salina and halobacteria are uniquely adapted to these harsh conditions.
High salt levels and intense sunlight stress these microorganisms. In response to this environmental stress, Dunaliella salina and halobacteria increase their production of carotenoid pigments. These pigments protect the organisms from harmful ultraviolet radiation and oxidative stress. This increased pigment synthesis under stress contributes to the intensity and permanence of Lake Hillier’s pink color.
Beyond the Color: Safety and Stability
Lake Hillier’s unusual color prompts questions about its safety. Despite its vibrant appearance, the lake is generally considered safe for human interaction. The microorganisms responsible for the pink hue are not known to be harmful to humans. Swimming in the lake would not pose a health risk.
The lake’s pink color is remarkably stable, unlike other pink lakes where the hue fluctuates with seasons or weather. Lake Hillier maintains its vibrant pink year-round, and the water even retains its color when collected in a container. This consistent coloration is attributed to the stable populations of the salt-loving microorganisms and the unique, isolated conditions of the lake. Located within the Recherche Archipelago Nature Reserve, its protected status helps preserve its pristine condition and extraordinary color.