Finding Coral's Ideal Environment

Part A: Ocean Temperature

When you think of coral reefs you probably envision a tropical location, sandy beaches, and brightly colored fish. This is not just because the travel industry has persuasive advertising. Corals reefs are only found in the regions of the ocean where the conditions are just right for zooxanthellae to photosynthesize and build up the limestone skeletons that form reef structures. Start your investigation of coral's ideal living conditions by exploring the ocean temperatures at which coral reefs are found.

1. Examine the map below of coral reef locations around the world. Each red dot on the map represents a reef.
   
   
   

   Image courtesy of NOAA.
   
   
   

   Checking In

   Answer the following questions to check your understanding of the global distribution of coral reefs.
   
   

   • Describe the global distribution of coral reefs. Are they evenly distributed throughout the world's oceans or concentrated in a particular region?
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     Coral reefs are concentrated in a band around the equator, between 30°N and 30°S latitude.
   • Describe where reefs are found in relation to land. Are they located primarily along coastlines, in the open ocean, or both? Are they evenly distributed among the world's oceans?
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     Reefs are mostly found closer to coastlines (including island coastlines) rather than further out in the open ocean. Reefs are more common in the Pacific and Indian Oceans than in the Atlantic.
   
   

   Stop and Think

   1: What do you think the observed distribution of coral reefs indicates about coral's favored environment?
   
   
2. Examine the map below of global sea surface temperature (SST). Compare the SST map with the coral reef distribution map above. Click on the SST map to open a larger image in a new window to help make the scale more visible.
   
   
   

   Global sea surface temperature (°C) February monthly mean 1982 - 1995. Image courtesy of NOAA - NWS Climate Prediction Center. Click image for larger view.
   
   
   

   Checking In

   Answer the following questions to check your understanding of corals' dependence on SST.

   • What is the range of ocean temperatures in the swath of ocean in which corals are most commonly found?
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     The region of ocean within 30° latitude above and below the equator has a temperature range of approximately 22-29°C.
   
   
   

   Stop and Think

   2: Do you think seasonal variations in ocean temperature affect coral reef health? Explain.