There Is a Lake Under the Ocean

Venturing deep into the Gulf of Mexico, scientists in submersibles have discovered a truly alien (Review) landscape: lakes and rivers that flow along the ocean floor. These are not made of water as we know it, but of an extremely salty brine, which can be four or five times saltier than the surrounding ocean. This hypersaline water is much denser than normal seawater, causing it to sink and pool in seafloor depressions. The boundary between the clear ocean water and the murky brine is so sharp that it creates an eerie, visible shoreline, sometimes with ripples on its surface just like a lake on land.

The formation of these brine pools is a story millions of years in the making. During the Jurassic period, a shallow sea in the area evaporated, leaving behind massive beds of salt up to several kilometers thick. Over time, these salt layers were buried by sediment. Being less dense than the rock above it, the salt pushed its way upward, creating large domes. When seawater seeps into these formations and dissolves the salt, it becomes super-saturated and emerges onto the seafloor as a heavy, toxic (Review) brine.

This bizarre feature earned the grim nickname 'the jacuzzi of despair' for a reason. The brine is completely devoid of oxygen and often saturated with toxic chemicals like methane and hydrogen sulfide. Any unsuspecting creature like a crab or fish that wanders into the pool is immediately overcome by the toxic shock, and its pickled remains are often preserved at the bottom. Paradoxically, while the pools are deadly, their edges are teeming with life. Mussels and specialized tube worms cluster around the brine, thriving on the chemicals and the bacteria that feed on them, creating a unique and extreme ecosystem in the dark depths.