The Salt Lake at Westgate Park in Port Melbourne turns pink almost every year due to a combination of things: high temperatures, plenty of sunlight & low rainfall. Apparently algae at the bottom of the lake in the salt crust produces a special pigment ( beta carotene) as part of its photosynthesis which causes the pinkish hue. The lake usually returns to its blue colour in the winter season or late autumn when temperature drops and rainfall increases..