Halobacteria (a form of Archea) thrive in water bodies with high salt content (at an optimal concentration of 20-25%), to the extent they are considered extremophiles. Crucially to Halobacteria’s ‘pink-ness’ they contain a pigment called bacteriorhodopsin that is used to absorb light in photosynthesis. However, with large blooms of halobacteria lakes can appear red or pink, as seen in the photo above.
The classic example of a lake showing this feature is Pink Lake (also known as Hiller Lake) in Western Australia; which is affected by Halobacteria cutirubrum and Dunaliella salina. The photo does not show a lake, though; instead it shows the salt ponds in San Fransisco Bay. These show the same bright colouring due to the same halobacteria as discussed earlier. The green pools contrast the pink ones both in colour and salinity, as the green has low salinity that allows green algae to thrive. The orange pool, however, holds its colour due to Brine shrimp, which generally occur in mid-salinities.