T. James Noyes, El Camino College The Environment Unit II (Topic 2A-2) – page 1 Name: The Ocean Environment Unit II: and Light (3.5 pts) Section:

Sound

Light goes through , but light is slowly absorbed by water until no more light is left. This is why the ocean gets darker and darker as one goes deeper into the ocean.

On land, an animal can see another animal in the distance long before it can hear the other animal. (Unless the animal is intentionally being loud.) In the ocean, animals will hear other animals coming long before they can see them. Since light does not travel as well through water as it does through air, eyesight is less valuable in the ocean and good hearing is more important.

Sound is transmitted much faster and better by solid objects. In other words, sound is absorbed less quickly by solids, so it goes farther before it is absorbed. Water is more “solid” than air, so sound travels faster and better in ocean water, making hearing more useful in the ocean than on land. For example, whale songs can travel thousands of miles in the ocean, allowing whales to communicate over vast distances. (There are certain depths in the ocean where the water carries sound better, and the whales use these layers to their advantage.)

Sound can also be used to “see” underwater. Dolphins emit high-pitched noises, and then listen for the echoes that bounce off objects. This is called echolocation, and is how our technology works. Dolphins listen for where the sound comes back from (its direction) and how long it takes for the sound to return (the farther away the object is, the longer it will take for the sound to return). Dolphins can not only determine the position of an object, but also tell what the object looks like, its shape.

1. Does sound travel better (farther, faster) through air or water?

T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 2

The Cause of Atmospheric Pressure and Hydrostatic Pressure

Pressure is, of course, caused when something presses or pushes against something else. In this class, we will primarily discuss atmospheric pressure and hydrostatic ocean pressure which are caused by the of the air and ocean water above an object. The basic rule is this: the more stuff (air or water) there is above, the higher the pressure on things below it. More stuff is heavier than less stuff. More air is heavier than less air. When we are up in the mountains, there is less air above us, so the weight of the air is less and therefore the air pressure is lower. When at , there is more air above us, so the weight of the air above us is greater and air pressure is higher.

The goes up pretty high. There is about 30 miles of air above our heads. We hardly notice the effects of the air pressure exerted by the atmosphere, because our bodies are built to tolerate it; it is “normal” for us.

Water, of course, is much heavier than air. Every 10 meters (33 feet) of water that is above your head is equivalent to the weight of the entire atmosphere. You really start to feel the water pressure, especially in your ears, when you dive towards the bottom of a pool, because there is more water above your head, so there is more weight pushing down, trying to push your ear drums into your skull.

Note: Sound waves are vibrations – fluctuations – in pressure. Sound waves slightly increase or decrease the pressure caused by the weight of the air and water above ocean organisms. Many ocean animals can feel these vibrations all along their bodies, not just in their ears or similar organs, and use the information to find food and avoid predators.

2. What causes pressure experienced by an object, the density of the air and water above, or the weight of the air and water above?

3. Where is there more air above your head, at the top of a mountain or at the beach (at sea level)?

4. Where is the air pressure higher, at the top of a mountain or at the beach (at sea level)?

5. Where is there more water above your head, inches below the surface of the water in a swimming pool or at the bottom of the pool?

6. Where is the water pressure higher, inches below the surface of the water in a swimming pool or at the bottom of the pool? T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 3

The Effect of the Ocean’s Hydrostatic Pressure on Living Things

To keep from being crushed by the pressure in the deep ocean, ocean animals fill their bodies with water and other which cannot be squeezed easily (unlike air). High pressure on your body squeezes gas (from the air in your lungs) into your blood. If you swim to the surface too quickly – that is, if the pressure outside you decreases quickly – then the nitrogen in your blood changes, forms bubbles, inside your body; there is no time for it to be squeezed back out of your body and into your lungs. This may cause (“rapture of the deep”) in which the nitrogen gas seems to act something like nitrous oxide (“laughing gas”) and thus makes feel good and impairs their reasoning. The good feelings are followed by sickness (“the bends”) in which nitrogen gas joins together to form bubbles in cavities like those in your joints and pinches nerves when you try to move. Humans can safely spend about 30 minutes at a depth of about 100 feet (30 meters) using SCUBA gear. The deeper you go, the higher the pressure and the quicker nitrogen is squeezed into your body, so you cannot safely spend as much time there. Deep-diving marine mammals have lungs like you and me, so they can also suffer from these effects, though they typically have adaptations to make them less harmful. For example, whales will squeeze air out of their lungs before diving.

Your Body on Coke If you experience the bends or , then your body is behaving like a carbonated beverage, for example a can of soda like Coca-Cola. dioxide was pushed into the under high pressure back at the Coca-Cola factory. This is what happens to the gases in your lungs when you dive; a gas is pushed into your body. When you open a can of soda, you are reducing the pressure on the liquid, allowing the gas to leave the liquid and form bubbles of gas within the liquid. The major difference is that the gas cannot escape your body, whereas bubbles rise up and out of the top of a can of soda. The more gas that escapes the can, the “flatter” the beverage gets. This is what also needs to happen inside your body for you to feel better: the gas has to escape, to go from your body back into your lung.

Atmospheric Pressure and

Atmospheric pressure can have a big impact on sea-level. Changes in the weight of the air above the ocean can raise sea level by over 3 feet beneath storms. The of storms can push this mound of water onto land, piling it

up until it is over 20 feet above sea level and flooding miles of the coast. This is called storm surge and is how overtopped the levees, pouring water into New Orleans, and how Superstorm Sandy did so much damage to New York and New Jersey. T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 4

The ocean is pushed down strongly beneath the higher air pressure outside the storm, so the ocean rises where the downward push is weaker: The water that is pushed down has to go somewhere. This is somewhat like a “see saw” or “teeter-totter”: if one end goes down, the other must come up. Examine the diagram showing the child, adult, and see saw. The adult weighs more than the child, so they exert greater pressure on their side of the see saw. The child’s side rises even though the child is exerting downward pressure too. The child weighs less, so they exert less pressure on their side.

Storm systems are associated with low atmospheric pressure, because the air in a storm system is warm, rising air. Warm air expands (gets “bigger”), so there is less air above each location (it has spread off to the side), and therefore less weight above each spot and thus less pressure above each spot within the storm.

Examine the picture on the right. The dotted line surrounds the air of the storm. Each black dot represents an air molecule. The arrows represent the air pressure at each location.

7. Is the air within the storm spreading out or being compressed together?

8. Does the expansion of the air within the storm increase or decrease the weight of the air above each spot within the storm? Where is the air pressure higher, below the storm or outside the storm?

9. Where will the ocean be pushed down more strongly, in a region of high atmospheric pressure or a region of low atmospheric pressure?

10. Does water get pushed from a place with high atmospheric pressure to a place with low atmospheric pressure, or does water get pushed from a place with low atmospheric pressure to a place with high atmospheric pressure?

11. Does sea level along the coast get higher where the winds are pushing water towards the coast or where winds are pushing water away from the coast? T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 5

Light and the Color of Objects

The color of an object depends upon both the atoms and molecules the object is made of AND the kinds of light shining on it, the colors of the rays of light that are striking it.

Sunlight includes ALL the colors of the rainbow: red, orange, yellow, green, blue, and purple. However, our eyes and brain only tell us about the strongest color of light coming from an object. We perceive the Sun as being yellow, because the Sun emits more yellow light than any other color, because more rays of yellow light come out of the Sun than rays of red, orange, green, blue, or purple light. Other hot objects like fire and light bulbs also emit all the colors of the rainbow, and may emit more of some colors of light than others.

Each substance absorbs some colors of light, and reflects other colors. The reflected rays of light “bounce off” the substance. As you can see from the picture below we see the color of light that reflects off an object most strongly. In the picture, the person looking at the shirt perceives the shirt as being “red” because mainly red light is reflecting off the shirt while other colors of light like yellow and blue are being absorbed. The shirt looks red, because more red light is coming from it than any other color of light.

The colors of light that are absorbed by an object make the object warmer. The energy in these colors of light is transformed into heat energy when the light is absorbed by the object.

12. Which colors of light are present in sunlight?

13. What is the strongest color of light in sunlight?

14. What color(s) of light does a green shirt reflect?

15. What color(s) of light does a green shirt absorb?

T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 6

Black and White Objects

If no light is entering our eyes, we see the color “black.” You probably already know this, but it is easy to check: Just turn off all the lights, cover your head, or your vision in some other way, and look around. This means that a black object does not reflect light; a BLACK object absorbs all colors of light.

If no color of light is much stronger than any other color of light, our eyes and brain tell us that the color of the object is WHITE. In other words, a white object reflects all colors of light about the same. White light is a combination or mixture of all the colors of light.

If one color of light is somewhat stronger than the others, then we perceive the object as having a “light” color. For example, a light blue shirt reflects all the colors of light pretty well, but the blue light a little better than the other ones. A pink shirt reflects all of the colors of light pretty well, but the red light a little better than the other ones. If only one color of light is reflected and only a little bit of it is reflected, then we perceive the object as having a “dark” color. A dark blue (navy blue) shirt absorbs all the colors of light well, but reflects a little blue light. A dark red (burgundy) shirt absorbs all the colors of light well, but reflects a little red light.

16. What color do we see if there is NO light coming from an object? (Hint: What color do you see when the lights are off?)

17. What color of light do we see if no color of light is strongest?

18. What happens to green light when it hits a white animal? Is it reflected or absorbed?

19. What happens to green light when it hits a black animal? Is it reflected or absorbed?

T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 7

Light in Ocean Water: Transmission and Scattering

Light on the red side of the rainbow is MORE likely to travel “straight” when it hits water molecules. Red light is Colors of the the color of light most likely to Rainbow travel “straight” when it hits in Order water molecules. Red Light on the blue side of the rainbow is MORE likely to “bounce off” in a random direction when it hits water molecules. We call bouncing off in a Orange random direction scattering. Blue light is the color of light that is most likely to scatter when it hits water molecules. Yellow

The other colors of light are somewhere in between red and blue light. The Green closer a color of light is to red in the rainbow, the straighter it goes through water. The closer a color of light is to blue in the rainbow, the better it scatters. Blue

20. After blue light, which color of light scatters most strongly off water Purple molecules?

21. After red light, which color of light tends to “go straight” down into the ocean instead of scattering off water molecules?

Light in Ocean Water: Absorption by Ocean Water

Light on the red side of the rainbow tends to be absorbed faster by ocean water. Red light is the color of light which is absorbed fastest by ocean water. This means that red light is absorbed quickly and thus does NOT go down very deep into the ocean before it completely disappears.

Light on the blue side of the rainbow tends to be absorbed slower by ocean water. Blue light is the color of light which is absorbed slowest by ocean water.

The other colors of light are somewhere in between red and blue light. The closer a color of light is to red in the rainbow, the faster it is absorbed. The closer a color of light is to blue in the rainbow, the slower it is absorbed, and the deeper it reaches before it is finally absorbed.

22. What color of light penetrates deepest into the ocean?

23. After red light, which color of light is absorbed most rapidly by water molecules? T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 8

Why the Ocean Looks Blue

We have learned that the color of an object or substance depends upon the strongest color of light we see coming from the object or substance. We have learned that blue light is the color of light which scatters most strongly in water and is absorbed slowest by water. Both of these contribute to the color of ocean water.

If you are standing at the coast, blue light is the color which is most likely to hit the surface and bounce off, to scatter, and enter your eyes, so you see the color blue when you look at the ocean. You do not see the colors Blue light bounces off to the side of light that go straight down. unlike the other colors that go straight. If you are beneath the surface of the ocean and look to the side, blue light is the color which is most likely to bounce off water molecules to the side, to scatter, and enter your eyes, so you see the color blue when you look to the side. Recall that red light tends to go straight, downwards in this case, so you will not see if it if you look to the side.

Because blue light scatters, blue light tends to take a pretty crazy path inside water. It scatters again and again and again.

If you are far enough beneath the surface and look upwards, you also tend to see blue light. Recall that blue light is absorbed slower than any other color of light, while red is absorbed fastest. This means that red light dies out first; it is completely removed from the environment. Then orange disappears, since it is absorbed second fastest. Then yellow is removed, and then green. Blue light is the last color to be absorbed, the color that is left behind once all the others are gone. So, everything tends to look blue since it is the only color in the environment in a significant amount and thus the only color that can scatter off water molecules or underwater objects. Blue light does not get absorbed as quickly as 24. Underwater everything has a “blue” tint. the other colors of light, so it penetrates deeper. Why do we see “blue” no matter what direction we look? Why don’t we see any other colors?

There is (A) ______blue light present underwater than any other color of light,

because blue light is absorbed (B) ______by ocean water than other colors of light.

In addition, blue light is shining in every direction you look, because blue light is

(A) ______easily scattered by ocean water than other colors of light.

Therefore, objects receive (A) ______blue light when underwater,

so underwater objects (C) ______(A) ______blue light,

making them look “bluer.”

Possible Answers: A: more, less B: faster, slower C: absorb, reflect T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 9

Purple Light

I often oversimplify in this class. Now, I am going to add a little complexity. I’m not going to test you on this, but I thought some of you might be wondering, what about purple light? Purple light scatters more strongly than blue light and is absorbed slower. Why isn’t the ocean purple? The Sun sends a lot more blue light to the than purple light. So even though purple light scatters more strongly and is absorbed slower, there is so much more blue light to begin with that blue light typically dominates over purple.

What about when the ocean looks green? What about other colors?

If there are lots of phytoplankton (tiny algae) in the water, the ocean looks green, because phytoplankton are green due to the green chlorophyll inside them. Green sunlight reflects off their green bodies and out of the ocean.

Like plants on land, phytoplankton use chlorophyll molecules to absorb and direct the energy to make food for themselves in the process we call photosynthesis. Note that some ocean algae use different colors of chlorophyll, colors other than green. There are red algae, golden algae, and brown algae. By the way, red are large groups of red-colored phytoplankton in the water.

Sometimes ocean water is brown. This typically indicates that there are lots of sediments, like mud, drifting in the water. It can also be the dead bodies of lots of phytoplankton.

If the water is shallow, the color of the ocean water may reflect the color of the ocean bottom. In other words, a muddy bottom makes the water look dark, and a sandy bottom makes the water look clearer. Of course, if this is the case, one is really seeing the color of the bottom, not the water.

Countershading

Notice that some ocean animals have a dark top or lighter- colored underside. This is called countershading. Striking examples of countershading include orcas (killer whales) and penguins.

Countershading helps predators who live near the surface of the ocean sneak up on their prey, and prey at the surface of the ocean avoid predators. If an animal looks down upon an animal with countershading, the dark top will look a lot like the dark water on either side and below it. The dark top will absorb the sunlight coming down, preventing it from being reflected upwards into the eyes of the animal looking downwards. If an animal looks up at an animal with countershading, the light-colored bottom looks something like the sunlight streaming down on either side of it. Its white belly does a good job of reflecting any light bouncing upwards off the water molecules and sending them back down just like the light coming directly from the Sun that is also heading down. T. James Noyes, El Camino College The Ocean Environment Unit II (Topic 2A-2) – page 10

Why Many Deep-Sea Animals are Red

You may have noticed that many deep-sea animals are red. Think of crabs, lobsters, and so on. What is so good about being red?

There is very little sunlight in the deep ocean. At a depth of about 500 feet (150 meters), only 1% of it remains, and sunlight is almost completely gone at 3300 feet (1000 meters). Blue light penetrates deepest, because the other colors (especially red) are absorbed more quickly by the ocean water. (Violet is absorbed more slowly than blue light, but there is so much more blue light to begin with that the blue light still dominates.)

Red is a great color for an animal to be if it lives far away from the surface, because little or no red light will penetrate deep enough to hit it; the red light will quickly be absorbed on the way down. Blue light that may penetrate down will be absorbed by its red body. Thus, any predators looking at the red animal will not see light coming from it, reflecting off of it. There is no red light to be reflected, and the blue light is absorbed, not reflected. Near the surface where there is some red light, the red light can reflect off the body of a red animal and into the eyes of a predator.

Even though sunlight does not penetrate deeply into the ocean, the ability to see – or at least sense light in some way – is an important adaptation for deep-sea life, because most deep-sea animals are bioluminescent: they use chemicals to create light. A reddish body still helps an animal stay hidden, because almost all animals make blue and green light. Again, any predators looking at the red animal will not see light coming from it, reflecting off of it. There is no red light to be reflected, and the blue light and green light are absorbed, not reflected.

25. Why are so many deep-sea animals red (crabs, lobsters, and many more)? How does this coloration help an animal blend in with the dark water of the deep ocean?

(A) ______light penetrates deeper into the ocean than any other color of light, because it is (B) ______(C) ______than any other color of light. If this color of light hits one of the RED deep-ocean animals, the light will be (B) ______by the animal’s body, so a predator looking at the animal will see the color (A) ______, and therefore have difficulty seeing the animal; the animal will blend in with the darkness found deep in the ocean.

Possible Answers: A: red, yellow, green, blue, black C: faster, slower B: absorbed, reflected, scattered