Pressure, Light and Sound
Pressure:
Increases with depth of water. On land we live under 1 atm (atmosphere) or pressure and sea level. This means that we have about 14.6 psi of weight from air above us. Marine organisms live under the weight of water and the atmosphere so the pressure is greater. Every 10m causes pressure to increase 1 atm. As pressure increases, gases compress/shrink. This creates problems for organisms that have air bladders, floats and lungs. This limits the depth range of many organisms.
Increases with depth of water. On land we live under 1 atm (atmosphere) or pressure and sea level. This means that we have about 14.6 psi of weight from air above us. Marine organisms live under the weight of water and the atmosphere so the pressure is greater. Every 10m causes pressure to increase 1 atm. As pressure increases, gases compress/shrink. This creates problems for organisms that have air bladders, floats and lungs. This limits the depth range of many organisms.
It also affects organisms from the deep that are brought to the surface. This is why it's often difficult to observe deep water organisms in a laboratory setting.
Light:
Light travels as waves thru air, space and water. Only a small part is visible to the human eye (known as "visible light"). The wavelength determines the color: longer wavelengths are red, shorter wavelengths are blue. Blue and green wavelengths are the only ones that can travel any distance in water.
Light waves travel faster in the air than in water which causes refraction upon entering the water (objects look "bent").
Lots of the sun's rays never make it to the surface due to reflection, scattering or absorption. Scattering is more likely in water than in air because of all of the dissolved substances it can bounce off of. As the waves are absorbed it is transferred into heat. Wavelengths are absorbed/transferred into heat at different times. The top meter absorbs 71% of red light. The order colors are absorbed/turned into heat energy is as follows: infrared--> red--> orange--> UV--> yellow--> violet--> green--> blue. This is the reason the ocean looks blue...because only blue "survives" to be reflected back to our eyes. By 300m all light has been changed to heat.
Light travels as waves thru air, space and water. Only a small part is visible to the human eye (known as "visible light"). The wavelength determines the color: longer wavelengths are red, shorter wavelengths are blue. Blue and green wavelengths are the only ones that can travel any distance in water.
Light waves travel faster in the air than in water which causes refraction upon entering the water (objects look "bent").
Lots of the sun's rays never make it to the surface due to reflection, scattering or absorption. Scattering is more likely in water than in air because of all of the dissolved substances it can bounce off of. As the waves are absorbed it is transferred into heat. Wavelengths are absorbed/transferred into heat at different times. The top meter absorbs 71% of red light. The order colors are absorbed/turned into heat energy is as follows: infrared--> red--> orange--> UV--> yellow--> violet--> green--> blue. This is the reason the ocean looks blue...because only blue "survives" to be reflected back to our eyes. By 300m all light has been changed to heat.
There are 2 zones in the ocean:
The photic zone: Surface zone that receives light (40-600m deep, with the average being about 100m). This is where all ocean photosynthesis takes place as well as gas exchange with the atmosphere-->very important to the ocean's food chains!
The aphotic zone: Lies in blackness; it is dark except light produced by living organisms.
The photic zone: Surface zone that receives light (40-600m deep, with the average being about 100m). This is where all ocean photosynthesis takes place as well as gas exchange with the atmosphere-->very important to the ocean's food chains!
The aphotic zone: Lies in blackness; it is dark except light produced by living organisms.
Sound:
Sound is a mechanical form of energy transmitted by rapid pressure changes. Sound intensity will decrease as it travels through the ocean due to spreading, scattering and absorption. The higher frequencies are absorbed sooner. Sound does travel better through water than light, so many animals use sound to "see" instead. Sound travels faster in water at the surface (due to increased temperature) as well as at great depths (due to increased pressure)
Sonar: (SOund Navigation And Ranging) is a technique that uses sound for navigation, detecting objects on/under the surface of the water or for communication.
Two types--Active & Passive
Sound is a mechanical form of energy transmitted by rapid pressure changes. Sound intensity will decrease as it travels through the ocean due to spreading, scattering and absorption. The higher frequencies are absorbed sooner. Sound does travel better through water than light, so many animals use sound to "see" instead. Sound travels faster in water at the surface (due to increased temperature) as well as at great depths (due to increased pressure)
Sonar: (SOund Navigation And Ranging) is a technique that uses sound for navigation, detecting objects on/under the surface of the water or for communication.
Two types--Active & Passive
Active sonar: Ships use this to search for objects in the ocean by sending sound out which creates an "echo" when it hits an object and sound waves return to the original source.
Experienced users can learn all kinds of things from the returning objects. Side-scan sonar (or multibeam), a type of active sonar, is dropped into the ocean and uses up to 60 transmitters/receivers to send out lots of sound waves at a time. |
Buoyancy:
Buoyancy is the ability to remain afloat in a liquid. Salt water has greater buoyancy because of its density. Since salt water has a great buoyant force it allows objects to float
Some organisms float on top of the ocean:
Due to seawater's higher density, an object is more buoyant in salt water than fresh water.
Buoyancy is the ability to remain afloat in a liquid. Salt water has greater buoyancy because of its density. Since salt water has a great buoyant force it allows objects to float
Some organisms float on top of the ocean:
- Portuguese Man-of-War (has balloon like floats)
- Sargassum, a brown algae, (has air sacs)
- Some fish produce oils to make them buoyant
Due to seawater's higher density, an object is more buoyant in salt water than fresh water.