What do Whales Need to Know about SCUBA Diving?

 

The most important detail in the instruction of new SCUBA divers is that they must breathe out all the way up during rapid ascent.  (SCUBA stands for Self-Contained Underwater Breathing Apparatus.)  At a 100 foot depth, the lung of a SCUBA diver contains four times as much air as it does at the surface, so three lungs full of air are exhaled on ascent.  Our instinct on a panic ascent is to hold our breath.  There is no sensation to compel exhaling.   Failure to exhale ruptures the lungs painlessly in an immediately fatal way.  Pearl divers and diving birds and animals do not have this problem because they take only one lungful of surface air with them when they dive since they have no pressure tanks for underwater breathing.  So, for this reason, nature had no motive to develop sensations and instincts in anticipation of this problem since this need is born out of man’s invention, not the needs of nature.  If you attempt SCUBA diving, pay very close attention to this portion of the instruction (unless you are a whale—see above).

 

Recently   sperm  whales, the deepest  diving   whales,  have  been  found   to have  bone  infarcts

(healing areas of devitalized bone) similar to the lesions seen in human divers who have had “the bends”.  The bends is a disease caused by ascending too rapidly after a deep dive.  A prolonged deep dive causes much nitrogen to dissolve in the blood of a diver whether human or animal.  On rapid ascent nitrogen bubbles will form large enough to obstruct capillaries where they happen to lodge, locally preventing the normal circulation of blood.  This event is especially painful when the obstructed capillaries are in bone---hence the name, the bends.  Is intense military sonar causing panic in sperm whales, disturbing their usual diving routines, and resulting in bone lesions not previously reported in these animals?  Nature did not equip whales with instincts to avoid this hazard (whales, duly note this part).  SCUBA diving aggravates this problem for us by permitting even longer and deeper dives, so another part of the SCUBA training is defining acceptable speeds of ascent  Even careful compliance with this training may not prevent the bends during air travel too soon after a dive (because of more bubbles released by the further reduction in pressure at altitude).

 

Before we as a group go ballistic about what high intensity sonar is doing to sperm whales’ bones, one among us who has access to appropriate specimens should get some sperm whale skeletal material from several decades ago suitable for seeking evidence of healed infarcts to compare with the extent of lesions observed in modern specimens.  I remember a case report from New York City a generation ago of a lady getting mercury poisoning from eating a reducing diet of mostly swordfish.  Some “gadfly” got permission from the Smithsonian to test a century or so old mounted swordfish for mercury.  The mercury content was almost identical to similarly mounted modern swordfish specimens.  Call this a constructive constraint on speculation. 

 

John A. Frantz, M.D.

Monroe City Council Board of Health

January 17, 2005