Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Deep sea fish - why should i be surprised?

  1. Oct 12, 2008 #1
    Well, many of you have seen a recent video of fish that live close to 5 miles under the ocean.


    As an organism, does anyone know what sorts of factors these fish are actually overcoming? The news article stated that the fish somehow don't have a swim bladder or 'lungs'. Is this is because having an air bubble this low would require an enormous amount of strength?

    Salt water has a density of 1.025g/cm3, and there are ~ 800,000 centimeters in 5 miles. so, for each section of square (cm2) centimeter of the fish, there are roughly 800 kilograms of water on top. Am I thinking logically? What must be the structural adaptations to adjust to this kind of force?

    They also said that at this pressure, electrical conduction along nerve axons stops working. Something doesn't sound right about this. I don't know how force or pressure works at the molecular level, but I don't see why pressure would affect the ability for the ion channels in the membrane of the axon to work, or the ability of the membrane capacitance to store charge/maintain voltage.

    Also, I wonder if the solubility of oxygen drops at that level of pressure. I would say 'no' because I'd think it was more about the stuff dissolved in the water like salts that would affect the amount of oxygen. On the other hand, the oxygen must have to diffuse down from the surface atmosphere, but I'm assuming that at equilibrium the oxygen would be relatively similar @ say 1,2,3,4 miles down.


  2. jcsd
  3. Oct 12, 2008 #2
    In the video, they mentioned that the fish eat shrimp. Well, shrimp have a nervous system, and they also use oxygen - why don't we care about them? There must be all sort of microorganisms down there too ... and we don't worry about them going 'pop'. :)
  4. Oct 12, 2008 #3


    User Avatar

    Staff: Mentor

    Pressure acts in all directions, so it doesn't require any kind of strength to swim at that kind of depth. Obviously, it isn't possible for any structure to withstand that kind of force if the force was unbalanced. Consider that scuba divers go down as far as 300 feet - how much pressure is that? And the only thing that complicates deep diving for people is getting the air mixture right and avoiding the effects of the decompression.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook