In Short

• Brine pools are ultra-salty, dense pockets of water that form lakes on the seafloor.
• Some pools are so low in oxygen and rich in toxic chemicals that they kill most animals that enter.
• Despite that, specialized microbes and mussels live right on their edges, thriving in extreme conditions.
• New brine pools discovered in the Red Sea may hold clues to past climate, geology, and even potential medical compounds.

What Exactly Is a Brine Pool?

A brine pool forms when extremely salty water, often associated with buried
salt deposits or chemical seeps, collects in low spots on the seafloor. The
water can be several times saltier than normal seawater, making it so dense
that it sits like a separate liquid with a visible surface and shoreline.

Remotely operated vehicles (ROVs) have filmed these pools in the Gulf of
Mexico and the Red Sea. They often appear as dark, shimmering ponds with
sharply defined edges, as if someone dumped a lake at the bottom of the
ocean.

The “Jacuzzi of Despair” and the “Hot Tub of Death”

One of the best-known brine pools sits in the Gulf of Mexico and has been
nicknamed the “Jacuzzi of Despair” or “Hot Tub of Despair.” The water is
both extremely salty and laced with hydrogen sulfide and methane. It has
almost no oxygen. Any fish, crab, or other animal that wanders in is
quickly killed and often preserved, effectively pickled by the brine.

Scientists exploring the area have observed dead crabs lying upside down
along the pool’s edge, apparently preserved there for years. The brine is
so hostile that almost nothing with gills survives inside it, even though
the surrounding seafloor looks fairly normal.

Life at the Edge: Mussels and Microbes

While the water inside the brine pool is lethal to most animals, the edges
can teem with life. Colonies of mussels grow along the boundary where the
toxic brine meets normal seawater. These mussels host chemosynthetic
bacteria that use methane or sulfur compounds from the brine as an energy
source, similar to the way bacteria at hydrothermal vents live off chemical
rather than solar energy.

Studies of these communities have shown that they form unique ecosystems,
with genetics and chemistry quite different from more familiar shallow-water
habitats.

New “Death Pools” in the Red Sea

In 2020, scientists exploring the Gulf of Aqaba (part of the Red Sea)
discovered a cluster of deep-sea brine pools now known as the
NEOM Brine Pools. Located at about 1,770 meters depth,
these pools are unusually close to shore and preserve sediment layers that
stretch back more than a thousand years.

Researchers have suggested that the extreme chemistry and unique microbes
in these pools could help scientists understand early Earth conditions and
maybe even provide leads for new medical compounds, including potential
cancer-fighting molecules.

Why Brine Pools Fascinate Scientists

Brine pools sit at the crossroads of geology, chemistry, and biology. They
reveal how salt deposits and fluid seepage shape the seafloor, they host
organisms that live off chemical energy instead of sunlight, and they act
as natural traps that preserve both modern animals and ancient sediments.

They also offer a preview of how life might exist on other worlds, such as
icy moons with subsurface oceans, where chemical gradients rather than
sunlight power ecosystems.

Sources

• Discovery – The Jacuzzi of Despair in the Gulf of Mexico
  
• LiveScience – Hot Tub of Despair: deadly ocean pool that pickles creatures
  
• Communications Earth & Environment – Discovery of the deep-sea NEOM brine pools
  
• University of Miami – Rare deep-sea brine pools discovered in the Red Sea
  
• Deep Sea News – Brine pools overview
  
• Science – Chemosynthetic mussels at a brine-filled pockmark in the Gulf of Mexico