Ocean Color Viewed from Space
What color is the ocean? The ocean reflects the color of the sky, but even on
cloudless days the color of the ocean is not a consistent blue. Phytoplankton,
microscopic plant life that floats freely in the lighted surface waters, may
alter the color of the water. When a great number of organisms are concentrated
in an area, the plankton changes the color of the ocean surface. This is called
a "bloom." This photograph shows such a change in color. It was taken by
astronauts aboard the space shuttle looking down at the coast of Angola.
Microscopic plant life is at the base of the marine food web and is the primary
food and energy source for the ocean ecosystem. Phytoplankton convert nutrients
into plant material by using sunlight with the help of the green pigment chlorophyll.
The chlorophyll pigments in the plants absorb light, and the plants themselves
scatter light. Together, these processes change the color of the ocean as seen
by an observer looking downward into the sea. Very productive water with a high
concentration of plankton appears blue-green. Very pure water appears deep-blue,
From space, variations in ocean color can be measured with sensitive instruments.
Ocean and land plants are green because chlorophyll absorbs red light but
reflects blue and yellow light. Satellite instruments measure the amount
of reflected light of different wavelengths. These amounts allow scientists
to estimate the productivity of Earth's land masses and oceans. The
false color images below show these
estimates of plankton distribution and productivity in the world's oceans.
False Color Images of Ocean Color
The sunlit surface layer of the ocean can be full of microscopic plants and animals.
As the legend shows, the red areas contain the most life, while the purple areas are
nearly empty of life. The number values on the scale indicate the milligrams of
phytoplankton per cubic meter of sea water. While the organisms are microscopic,
large numbers result in a measurable mass when filtered from the water. Ocean areas
of high productivity support more life than less productive areas. It is as simple
as more food = more fish. More oxygen is produced and carbon dioxide consumed in
these highly productive areas of the ocean.
|Click on the map to see a larger view
The plankton populations are dependent on a variety of factors, including ocean
currents, temperature, availability of nutrients, amount of sunlight, and ocean
depth. Many different species of plankton contribute to ocean color, although
only a few species, occurring in great numbers, are found at any one time or place.
The individual plants live at various depths, from the surface to nearly 100 meters,
but prefer the surface sunlit regions with sufficient light to support photosynthesis.
In the ocean, as on land, plants are the foundation of the food chain
on which all other organisms depend. The productivity of the ocean is very important
to human activities and to the overall health of the planet. Remote-sensing of the
productivity of the oceans through the use of instruments aboard satellites helps us
better understand this vast frontier.
- Print out a blank map and outline the ocean regions with
higher productivity. Consider the colors in the legend from green to red to be
areas high in productivity. Color these areas red on your map using a colored
pencil, pen or crayon.
- Color the lesser productive areas on your map in blue.
- Compare/contrast productivity near the coastal areas with that in the
- Compare the productivity of ocean water near the equator with that in the
northern and southern latitudes in these areas:
- in the mid-Atlantic
- in the mid-Pacific
- eastern coastline of North and South America
- western coastline of North and South America
- western coastline of Asia
- In the region of the equatorial Pacific, where is the ocean most productive?
- In the region of the equatorial Atlantic, where is the ocean most productive?
- Compare/contrast the productivity in the oceans in the northern and southern hemispheres.
- Can you think of any factors that cause the differences?
- Predict at least three factors that affect the productivity of the oceans.
Variations in "greenness" in the image show the productivity of plant life on
the continents. This is also a false color image.
The image shows both the ocean and the land productivity
by detecting variation in the presence of the pigment
chlorophyll (the green coloring in plants) using remote-sensing instruments aboard satellites.
Continental Vegetation Detected from Space
|Click on the map to see a larger view
As you record your observations focus on the land areas.
- Locate and label these areas of high productivity on your map. Color
them in green.
- Amazon Rainforest in South America
- Congo Rainforest in Africa
- New Guinea in Southeast Asia
- the southeastern USA in North America
- What are some of the similarities and differences of these regions?
- Locate and label these areas of low productivity on your map.
Color them in brown.
- the Sahara Desert in Africa
- the Australian Desert
- the Arctic Tundra in Northern Alaska
What are some of the similarities and differences of these regions?
- Predict at least three factors affecting the productivity of the land masses.
Do these factors explain the differences you observed?
On land, we can judge the productivity of an environment by observing its "greenness."
Tropical rain forests are more productive than deserts or arctic tundra.
These differences in color can be observed from space.
From space, sensitive instruments can measure variations in amounts of reflected light.
This data is then mathematically sorted with formulas that estimate productivity
from the measurements. False color images are produced
like those you have examined in this lesson. The images indicate the presence of
plants through detection of the plant pigment clorophyll. Photographs taken from
space can show differences in the productivity of the land and oceans, but not with
the precision and detail that the false color images yield.
shows the distribution of plant life on Earth from satellite measurements in space.
As the movie plays and Earth rotates, observe the pattern visible in the different
latitudes. Make some generalizations.
Images and movie from
Tell us what you think about this page.
Thu Jul 27 10:15:02 1995