2A_3 – Slide 1
Topic 02A:
The Ocean Environment,
Part III
Online Lecture:
Light in the Ocean
& Organisms’ Coloration
Light
vs. Sound
Eyesight is not as useful:
water absorbs light faster than air.
Echolocation
Demonstration:
Sound in a
solid vs. air.
2A_3 – Slide 2
Darker down here =
light is absorbed near the
surface so less gets down here
Hearing is more useful in the ocean:
sound travels faster in water and
is absorbed less quickly than in air
Countershading
Turtle: No
Countershading
2A_3 – Slide 3
Looking Up From Below
Looking Down From Below
White Belly/Bottom
Black Top
Light and Color
2A_3 – Slide 4
○ Sunlight includes all the
colors of the rainbow
– our eyes only tell us about
the strongest color of light
coming from an object
○ Each substance absorbs some colors of light,
and reflects other colors (they “bounce off”)
– the colors of light that reflect off the object
are the colors that we see with our eyes
– black if no light comes from an object
– white if no color is the stronger than the others
What color shirt should you wear on a hot day? Why?
e.g., Color of Shirts
2A_3 – Slide 5
In each case, which colors are absorbed
and which colors are reflected?
Remember: Sunlight contains all colors of
the rainbow. Yellow is just the “strongest.”
Water and Light
Before Going
Through Water
Through
Water
2A_3 – Slide 6
2A_3 – Slide 7
Blue Wherever You Look
○ Ocean water scatters (“reflects”)
colors on the blue side of the
rainbow more easily than colors
on the red side of the rainbow
– the “redder” colors
go straight down
while blue light
bounces off water
molecules and into
your eye (just like a
blue shirt is “blue,”
because blue light
reflects off of it)
scattered
absorbed
not scattered
(goes straight down)
Ocean water can look green or
brown if “stuff” is in the water.
Blue is the Only Color “Left”
2A_3 – Slide 8
○ Ocean water absorbs
the colors on the red side
of the rainbow faster than
it absorbs the colors on the
blue side of the rainbow
– the other colors of light
absorbed
are absorbed first,
so blue is the
Very little red
only color “left”
Some green
Lots of blue
Overall Color:
Light Blue
scattered
Blue
Ocean
Lighter/Whitish
all colors still present
Blue
2A_3 – Slide 9
Red
Red
Blue
NOAA/Dept. of Commerce
Darker/Bluish
Water absorbs the red light
blue is the only color left,
(it disappears), but the blue light
and there is not much of it
“scatters” (reflects, bounces off)
water molecules and into our eyes.
Why are Many Deep-Sea Organisms Red?
2A_3 – Slide 10
○ Which color of sunlight penetrates Blue
deeper into the ocean, blue or red?
○ When this color hits the body of
a red animal, will it be reflected
or absorbed?
Absorbed
Absorbed
○ What color will a predator see
if it looks at the red animal?
Does this make the animal
stand out or blend in?
No light bounces off,
so predator sees black.
NOAA/Dept. of Commerce
Red animal blends in
with the dark water.
Seeing
Red Organisms
in the Ocean
There is no red light in
the deep ocean, so no
light bounces off red
animals and into the
eyes of a predator.
Many deep-ocean animals
are bioluminescent, but
blue-green light doesn’t
help them see red animals.
2A_3 – Slide 11