 Part
1: The color of water
Everyone knows the sea is blue--whether you look from above
or below. But if you look at the ocean carefully, you can often see traces
of other colors: brown, green, even red or yellow.
At the same time, if you get a small bottle of clean ocean
water and hold it up to the light, it will appear clear and colorless.
What's going on? |
Water, it turns out, is like a colored filter. The filtering
effect is weak enough so that you can't really see it acting on light passing
through a small bottle of water. Dive to the bottom at the Flower
Garden Banks -- or a swimming pool -- and look up and the blueness of
the water will become obvious.
Other colors in water are caused by impurities like soil,
algae, or natural dyes like tannin, that are in the water. So the bluest
water is usually the cleanest water in locations far from land or along
coasts where there is little runoff from rivers. The clear blue water of
the Flower Garden Banks are a sign of their location over 100 miles south
of Texas and Louisiana. |
(Above) The manta ray's distinctive shape appears as a black shadow
against the blue surface water.
Like the manta ray at the top of the page, this whale shark lives
by filtering floating plankton.
The plankton it eats are part of a food chain that depends on ligh
energy from the sun. |
