### Lake Hillier
Australia — Ringed by dark forests and the ocean, this extremely salty lake looks exactly like a giant, bubblegum-pink milkshake.
For decades, scientists thought this hypersaline (extremely salty) lake got its bizarre color from a single type of algae. But a massive 2022 metagenomic study proved that Lake Hillier is actually a massive team effort. The pink hue is created by a diverse consortium of polyextremophiles—microscopic survivalists adapted to multiple deadly conditions.
To survive the intense Australian sunlight and toxic salt levels, bacteria like Salinibacter ruber and archaea like Halorubrum work together like a microscopic pigment factory. They pump out massive amounts of red and orange carotenoid pigments, which act as a heavy-duty biological sunscreen for their cells. Millions of these tiny organisms dye the entire lake an opaque, milky pink.
However, the lake isn't magically pink forever. It depends on the salt stress to keep the microbes churning out their colorful sunscreen. In 2022, extreme rainfall flooded the lake with fresh water, diluting the salt. The microscopic crew took a break, and the lake temporarily turned a pale blue-grey until evaporation slowly cranked the salt levels back up!