SMS 204: Physics for Marine Sciences
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Physics of diving
What in physics pertains to diving?
Forces –buoyancy, gravity, hydrodynamic (currents), pressure x area.
Physics of gasses in fluids (solubility).
Sound and light in the environment and our perception of them.
Heat exchange with medium.
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What organisms, that are not fish and are derived primarily from land organisms, are engaged in diving?
sea snakes, sea turtles, the marine iguana, marine
crocodiles, pinnipeds (sea lions, fur seals and seals), cetaceans (whales and dolphins), sea otters, manatees and dugongs (sea cows).
Most dive shallow (<10m).
Some dive deep:
Emperor pinguins: 400-500m
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Dive pattern of an elephant seal female:
Elephant seals dive continuously, day and night, for periods at sea lasting 2–8 months. They spend 90% of the time at sea submerged, averaging 20min per dive (with maximum dive duration’s of up to 2 hr) and spend less than 3min at the surface. They often feed at 300<depths <600 m, occasionally diving deeper than 1600m.
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Recently, beaked whales have been found to routinely forage at depths far greater than any other air-breathing vertebrate. They
routinely foraged to 1070 and 835mand stayed submerged for an average of 58 and 47 min with a maximum depth and
duration of 1888 m and 85 min.
All of these animals face the same fundamental constraints:
1. increased pressure .
Adaptations to pressure address the mechanical effects of pressure, and with the increased solubility of gas (N2 and O2) as the pressure increases.
2. Lack of oxygen associated with breath hold diving.
Adaptations centre around modifications in metabolism, blood flow and oxygen storage capability.
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Henry’s law – gas solubility in relation to pressure
How much gas can we incorporate into blood and tissue of a marine organism (gas is the solute and tissue is the solvent)
Solubility increases with pressure and decreases with temperature.
For marine mammals both will contribute to more solubility as they dive (deep waters are typically colder (not always in arctic regions and pressure increases significantly).
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Scuba diving and gas solubility
The problem is mostly with nitrogen, which is not involved in metabolism.
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Free divers, as marine mammals, do not breath pressurized air, reducing the incidence of DCS.
However, apparently stress can induce DCS.
There also seems to be some physiological adapations which prevent full solubility of nitrogen from occurring in free diving organisms (separation of gases into different compatments).
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What about hypoxia (oxygen deprivation)?
Adaptations:
Higher oxygen carrying capacity due to 1. blood volume and 2. hemoglobin concentrations. In addition, some marine mammals contract their spleen during dives to release a store of oxygen-rich blood cells into the circulation. To avoid blood clots resulting from such high concentrations of red blood cells, many species lack a key clotting factor found in other mammals.
increased concentrations of oxygen-carrying proteins such as myoglobin in heart and skeletal muscles and neuroglobin and cytoglobin in the brain.
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Frontier: sensors strapped to diving organisms.
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How is the light and sound environments different under water than above water?
Speed?
Attenuation?
Spectra (frequency content and change)?
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How about heat exchange?
Significantly higher in water than in air (why?) -> hypothermia.
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What physical concepts we have learned do you think matter for surfing?
Momentum, energy (wave), forces (gravity, buoyancy), Torque, hull speed, balance (center of gravity vs. center of buoyancy).
When we wait for the ‘right’ wave, what are we doing?
Physics of surfing
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https://topex.ucsd.edu/ps/energy.pdf
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Breaker wave height is related to depth and speed
or H/L>1/7
https://topex.ucsd.edu/ps/energy.pdf
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Balance of forces:
https://annex.exploratorium.edu/the-world/surfing/physics/surfsci2.html
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Summary of class
Physics provide a useful lens from which to understand marine organism adaptation to the environment in which they operate.
Evolution provide the time scale for those adaptation and ‘solves’ the most likely constraints.
Successful adaptations have appeared in different phyla at different times seemingly unrelated (e.g. bioluminescence).
I hope you found something in this class you want to know more about…