Explain to me high pressure as it relates to organisms of the deep

What affect, if any, does the ocean pressure of the deep have on organisms living there?

I ask this because an NPR story this morning talked about current unmanned expeditions happening in the Mariana Trench. The story spoke about investigating the life that can be found in the deepest part of the ocean, and also talked of the extremely high pressure, as though that pressure has some effect on the life found there.

Wouldn’t the organisms living in the deep “feel” nothing? Aren’t their bodies in full equilibrium with the surrounding pressure of their environment?

I understand why the discussion of the high pressure is relevant, since it definitely impacts the design of instruments sent to investigate the deepest part of the oceans. But I think for life living there, it really isn’t relevant.

Can anyone elaborate?

Pressure plays a role in the type of life that can be found in the deepest parts of the ocean. Perhaps that is what they were trying to say. Different types of life are going to be found down there where the pressure is great than up where the pressure is less. We’re not going to find any dolphins down there, for instance.

Yes - a conspicuous shortage of air-breathing life forms can be expected below -20,000’.

But the extremely low compressibility of water (as compared to the surface, something like 5% at the depth of the Marianas Trench) means that water pressure is something that animal tissues don’t need extreme adaptions to tolerate.

Its the cell membrane that gets effected the most. Wikipedia entry for Piezophile.

Quote : * The high pressures experienced by these organisms can cause the normally fluid cell membrane to become waxy and relatively impermeable to nutrients.*

Here are some of the other adaptations they make.