On an island off the southern coast of Western Australia lies Lake Hillier, renowned for its stunning pink color, resembling a strawberry milkshake. However, experts advise against trying to drink it, as Lake Hillier is ten times saltier than ocean water.
Previously, many studies suggested that the pink water was due to a type of salt-loving algae known as Dunaliella Salina thriving in the lake. This algae contains a pigment called beta-carotene, which is also found in carrots. However, in 2015, Dr. McGrath, working on the Extreme Microbiome Project, which utilizes gene sequencing to study organisms in extreme environments, made a surprising discovery.
Australia is home to many pink lakes.
“We confirmed that the algae D. Salina is present in Lake Hillier, but in very low quantities. What we found was a type of bacterium called Salinibacter Ruber. Over 20% of each DNA segment we obtained from the lake was from bacteria, while less than 0.1% of the DNA was from algae,” he stated.
The bacterium Salinibacter Ruber contains a pigment called bacterioruberin, which is much pinker than beta-carotene.
After his research trip, Dr. McGrath placed a souvenir bottle of water from Lake Hillier on his desk and noticed something remarkable.
There was a window on one side of his desk, and after some time, he observed that the algae – which had little tails and could wriggle towards the sunlight – moved to the side of the bottle that was illuminated.
“But the remaining water still maintained its pink color,” he said, adding that this was clear evidence that it was the bacteria, not the algae, that gave Lake Hillier its pink hue.
While Australia has several pink lakes, not all of them retain their pink color as consistently as Hillier. There is a lake near central Melbourne that was once pink but has now turned a deep blue. Expert Martin Watts from Parks Victoria noted that a dry heatwave seemed to change its color to pink. “It’s a natural phenomenon that occurs when high temperatures cause the evaporation of freshwater components from saline water. The last time it turned pink was in April 2019.”
According to environmental scientist Tilo Massenbauer, pink lakes are created by a combination of various factors including the climate and hydrology of this ancient continent, such as rising temperatures, high salinity in the water, sunlight exposure, and low rainfall. Additionally, the D. Salina algae are green; however, in environments with high salinity and intense sunlight like Lake Hillier, the algae must rely on beta-carotene for photosynthesis, which can turn the algae red, causing the surrounding water to appear pink.
