Initial Publication Date: August 12, 2008

Finding Coral's Ideal Environment

Part B: Ocean Depth

Temperature is just one measurable quantity that can be used to characterize coral reefs' favored environment. Ocean depth is another important factor in determining why coral reefs are found in specific areas of the world. Continue your investigation by exploring ocean depth.

Examine the combined bathymetry (ocean depth) and topography (land surface features) map below. Take a minute to familiarize yourself with the color-coded elevation (height) scale.

Image courtesy of NOAA. Click image for larger view.
Checking In
Answer the following questions to check your understanding of bathymetry and topography.
- Why are there negative values on the elevation scale? What does an elevation of zero mean?
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The scale on the bathymetry map covers such a wide range of values that it is extremely difficult to make a precise depth measurement of how deep coral reefs really live. To get a little more insight, let's look at another classification guide. Based on two variables, one of which is depth, the ocean is divided into three zones: aphotic, euphotic, and dysphotic. These names derive from Greek prefixes and root words. Below are the definitions of the root and prefixes.

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Using what you understand about the words, try to match the location of these zones on the image above.

4. The three ocean zones are determined by depth and what second variable?

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Stop and Think

3: Do coral reefs seem to favor deeper or shallower waters? (Refer back to the map of coral reef locations in Part A if necessary.) Based on what you know about the life processes of coral, explain why you think coral reefs thrive at these depths.

3. Examine the image below. This graph is a representation of how deep light of each color of the visible spectrum penetrates below the ocean surface.