69
chapter four
Pressure regulation
Sascha K. Hooker and Andreas Fahlman
4.1 The big picture challenge and summary
Marine mammals dive to find their food but have to return to the surface to breathe. Some
species occupy relatively shallow foraging niches, while others have adapted to target prey
deep in the ocean. Diving records for elephant seals exceed 2000 m, and beaked whales have
been recorded to dive as deep as 3000 m. Although management of available O 2 has been the
focus of diving research for over 70 years, relatively little effort has been dedicated toward
understanding the effects of elevated pressure on marine mammals. Pressure is an important
thermodynamic variable that, like temperature, can have significant physiological implications. Marine mammals are thought to have various anatomical and biochemical adaptations
to help them to withstand the pressure at depth, in particular, reducing any body gas-filled
spaces, and allowing their chest and respiratory system to compress to the limit of collapse.
Contents
4.1 The big picture challenge and summary ......................................................................... 69
4.2 Current knowledge .............................................................................................................. 70
4.2.1 General abilities of marine mammals .................................................................. 70
4.2.2 Physics of pressure, gas volume, and solubility .................................................. 72
4.2.3 Pressure, biochemistry, and blood flow ............................................................... 73
4.2.4 Pressure and airspaces ............................................................................................ 74
4.2.5 Lungs and diving lung collapse ............................................................................ 74
4.2.6 Diving diseases ........................................................................................................ 78
4.2.6.1 High pressure nervous syndrome and nitrogen narcosis .................. 79
4.2.6.2 Oxygen toxicity .........................................................................................80
4.2.6.3 Decompression sickness...........................................................................80
4.2.6.4 Shallow-water blackout ............................................................................ 81
4.3 Tools/methods used for this field ..................................................................................... 82
4.3.1 Animal-attached dive recorders ............................................................................ 82
4.3.2 Observation of lung structure and dynamics .....................................................83
4.3.3 Measurement of blood flow, gases, and bubble formation ................................84
4.4 Future of this topic ...............................................................................................................85
4.4.1 Phylogenetic variation .............................................................................................85
4.4.2 Form and function ...................................................................................................85
4.4.3 Consideration of alternatives ................................................................................. 86
Glossary .......................................................................................................................................... 86
References ....................................................................................................................................... 87
chapter four
Pressure regulation
Sascha K. Hooker and Andreas Fahlman
4.1 The big picture challenge and summary
Marine mammals dive to find their food but have to return to the surface to breathe. Some
species occupy relatively shallow foraging niches, while others have adapted to target prey
deep in the ocean. Diving records for elephant seals exceed 2000 m, and beaked whales have
been recorded to dive as deep as 3000 m. Although management of available O 2 has been the
focus of diving research for over 70 years, relatively little effort has been dedicated toward
understanding the effects of elevated pressure on marine mammals. Pressure is an important
thermodynamic variable that, like temperature, can have significant physiological implications. Marine mammals are thought to have various anatomical and biochemical adaptations
to help them to withstand the pressure at depth, in particular, reducing any body gas-filled
spaces, and allowing their chest and respiratory system to compress to the limit of collapse.
Contents
4.1 The big picture challenge and summary ......................................................................... 69
4.2 Current knowledge .............................................................................................................. 70
4.2.1 General abilities of marine mammals .................................................................. 70
4.2.2 Physics of pressure, gas volume, and solubility .................................................. 72
4.2.3 Pressure, biochemistry, and blood flow ............................................................... 73
4.2.4 Pressure and airspaces ............................................................................................ 74
4.2.5 Lungs and diving lung collapse ............................................................................ 74
4.2.6 Diving diseases ........................................................................................................ 78
4.2.6.1 High pressure nervous syndrome and nitrogen narcosis .................. 79
4.2.6.2 Oxygen toxicity .........................................................................................80
4.2.6.3 Decompression sickness...........................................................................80
4.2.6.4 Shallow-water blackout ............................................................................ 81
4.3 Tools/methods used for this field ..................................................................................... 82
4.3.1 Animal-attached dive recorders ............................................................................ 82
4.3.2 Observation of lung structure and dynamics .....................................................83
4.3.3 Measurement of blood flow, gases, and bubble formation ................................84
4.4 Future of this topic ...............................................................................................................85
4.4.1 Phylogenetic variation .............................................................................................85
4.4.2 Form and function ...................................................................................................85
4.4.3 Consideration of alternatives ................................................................................. 86
Glossary .......................................................................................................................................... 86
References ....................................................................................................................................... 87