Diving Pressure

From: Kim Marshall (kimm@oceanalliance.org)
Date: Sun Dec 15 2002 - 12:50:51 EST

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    Question:
    I have been wondering about how deep sea animals survive under such high
    pressure; more specifically how they behave. I already know the basics about
    swim bladders and how only deep sea subs like Jason can reach that far down,
    but nothing in detail. Thanks for all your help.
     
    Reply:
    Marine mammals can dive to great depths without suffering from the adverse
    pressure of the ³bends: because they have a greater ability to transport
    oxygen across lung membranes, have a higher percentage of oxygen in their
    blood, and a high carbon-dioxide tolerance. During deep dives these animals
    reduce their heart rate (bradycardia) and peripheral blood flow and
    circulation to all areas except the heart and brain.

    Cetaceans can exhale as much as 88% of its lung air with a single breathe
    (humans approx. 12%). They also collapse their lungs at about 100m which
    prevents the absorption of nitrogen into the blood, thereby preventing the
    bends. Oxygen use is reduced and heat loss inhibited. They regain the
    ability to dive by maximizing cardiovascular and respiratory activity at the
    surface by varying breathing techniques.

    These adaptations to the respiratory system have allowed deep diving in
    mammals. They do not suffer apnea or asphyxia from lack of oxygen, and they
    avoid decompression sickness despite the retention of air within the
    respiratory system.
     
    While recovering from a dive, cetaceans (whales, dolphins, and porpoises)
    and pinnipeds (seals, sea lions, and walruses) breathe by exhaling and
    inhaling very rapidly at the surface. Neither animal dives on residual lung
    volume. To restrict nitrogen absorption these animals can transfer alveolar
    air into cartilage-supported airways. Diving mammals probably have
    reinforced bronchioles for shunting of pulmonary gas away from the
    respiratory capillaries at depth.

    References:
    1. Harrison, R.J., Functional Anatomy of Marine Mammals, Academic Press:
    New
    York, 1974
    2. Leatherwood, S., Reeves, R., Whales and Dolphins (The Sierra Club
    Handbook), 1983

    Also go to WhaleNet¹s search section to find other replies to this type of
    question at http://whale.wheelock.edu/Search.html.

    Happy Holidays!
    Kim

    Kim Marshall
    Executive Director
    Ocean Alliance (Whale Conservation Inst. & the Voyage of the Odyssey)
    191 Weston Road, Lincoln, MA 01773
    781.259.0423 ext. 14 fax 259.0288
    www.oceanalliance.org www.pbs.org/odyssey
    Please support our efforts to conserve whales and their ocean environment
    through research and education :)



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