According to David Kennedy, coastal geomorphologist and associate professor at the University of Melbourne, salt lakes turn pink as a result of algae called Dunaliella Salina, which is found in sea salt fields, though Kennedy says there’s research that suggests bacteria can play a small part in the pink hue.
Some Australian salt lakes are hypersaline (landlocked and super salty) which isn’t an easy place for algae to live. Dunaliella Salina is what they call an extremophile, which means it thrives in environments that others usually can’t tolerate – like, say, the bottom of a salt lake. “The pink colour occurs when the salt content starts to increase,” says Kennedy. “The algae can happily tolerate salt levels of up to 28 to 35 per cent [by comparison, seawater is around 3.5 per cent] therefore the lakes tend to turn pink when salt levels increase which occurs in hot, dry conditions.”
Australia has a high number of pink lakes due to our climate. “Put simply, we’re hot and dry with little rainfall,” says Kennedy. “Also the ancient age of the continent also means there is a lot of salt in the landscape.” But not all salt lakes turn pink – it’s got to be the right climate for it. Rainfall and fresh groundwater can dilute a salt lake, which often means that the pink algae can’t thrive as much.