Sue Zupko: 9 Under the Sea

NOAA Teacher at Sea: Sue Zupko
NOAA Ship: Pisces
Mission: Study deep water coral off the east coast of FL
Geographical Area of Cruise: SE United States from off Mayport, FL to Biscayne Bay, FL
Date: June 3, 2011

Weather Data from the Bridge
Position: 29.1°N 80.1°W
Wind Speed: Light and variable
Wind Direction: 112 true
Visibility: 10 n.m.
Surface Water Temperature: 28.6°
Air Temperature:28.2°
Barometric Pressure:1015.3
Water Depth: 82 m
Salinity: 36.5
Wet/Dry Bulb: 28.2/24.5

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I was reminded on this voyage that colors change at depth in the ocean.  If you were swimming at 60 feet, you wouldn’t see reds.  Jana said she cut her leg while diving a few years ago at 60 feet.  She watched the blood coming from the cut and it was black to her eye.  Knowing it was probably wise to come to the surface with a cut like that in the open ocean, she started ascending (coming up).  At 30 feet she stopped to look at her cut.  The blood was green.  Is Jana a Vulcan?  As she rose to the surface, she continued to watch her blood flow from the cut.  At the surface, finally, the blood was red.

Light is interesting.  The white light we see has all the colors coming from it.  When you think of the rainbow, red has the longest wavelength, and the lowest energy.  When your friend is wearing a red shirt, you are actually seeing the red wavelengths reflecting (bouncing) back to hit your eye.  So, your mind sees red.  It doesn’t mean you’re angry (Get it? That’s a joke).  However, in water, particles, such as detritus and plankton,and the water itself, get in the way and block or absorb the wavelengths.  Since red has low energy, it gets interfered with quickly.   The shorter, higher-energy blue wavelengths can reach down farther.  Now, think back to our Big Eye example.  He’s red.  However, at depth he looks black and is camouflaged against the background of dark rocks and shadows.

Try this at home.  Take a red or blue transparent bottle.  I have a red water bottle that I can see through.  Put a blue object behind it such as an internet cable or a shirt.  What color does the object appear to be now?  I’ll bet a really dark purple or a black.  You might try a blue transparency over a red picture.  One of my students, Kaci, was creating a PowerPoint slide show.  His background was patriotic with red, white, and blue stripes.  He wanted to pick a contrasting color to continue the patriotic theme of red, white, or blue.  As a solution, he chose a transparent rectangle as a background to dark blue letters.  The colors turned out a bit strange in the background and he had to fiddle with his transparency a bit.  That is similar to the fish color being distorted by the water when there is little light at depth.

When the ROV (Remotely Operated Vehicle) shines its light on the fish, we see the real color of the Big Eye. There is very little distance for the water and particles in the water to distort the red color.  The LED (Light Emitting Diode) headlights on the ROV have a powerful beam so we can see the real color of the fish.

To read more on how color works in water, click here.