How do fish survive the intense pressure of deep water?

The deep ocean is a harsh environment. At 11 kilometers below, water at the Mariana Trench exerts eight tons of pressure per square inch. This is 1,100 times greater than the pressure at sea level on dry land. 

Under this type of pressure, the normal tetrahedron shape of the water molecule is warped. Inside of an organism, this change in water molecule shape prevents biological processes from taking place, thus killing the organism. New research from the University of Leeds shows how fishes living at these depths survive otherwise crushing pressure.      

“Life has adapted to survive and thrive in environmental extremes. In the depths of the oceans, organisms live under extreme high pressures that would destroy human life,” said Professor Lorna Dougan.

“These high pressures distort the liquid water that resides in all life, resulting in detrimental impacts to the biomolecules that underpin all biological processes.”  

“We need to understand what happens to water under pressure and how pressure-adapted organisms combat these effects. If we can understand how these organisms survive at extreme pressure, we can apply these findings to the wider study of biomolecular stability.” 

The chemical that allows fish to survive these depths is TMAO – trimethylamine N-oxide. The research shows that the amount of TMAO in ocean dwelling animals increases with the depth they live at. 

Led by Dr. Harrison Laurent, the researchers fired a beam of neutrons at water particles under low pressure (25 bar) and high pressure (4 kbar) with and without TMAO present. Without TMAO, the water bonds became distorted and compacted. With TMAO, however, the water bonds were strengthened and supported.

“The TMAO provides a structural anchor which results in the water being able to resist the extreme pressure it is under. The findings are important because they help scientists understand the processes by which organisms have adapted to survive the extreme conditions found in the oceans,” said Dr. Laurent.

This research allows scientists to better understand how a plethora of newly discovered organisms can survive deep in the world’s oceans. The study is published in the journal Communications Chemistry.

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By Zach Fitzner, Earth.com Staff Writer