Exercise 1

Objectives

Students learn to read and interpret the distribution of physical phenomena on a global map.
Students learn how to work with a basic GIS programme.

Materials

• Download the worksheet Global distribution of coral reefs - What do corals need? (5 MB .rtf file)
• Internet access

Procedure

To localize the areas where corals occur, open the following site: https://catalogue.odis.org/view/612
Go to 'Maps - Location of coral reefs'. Switch on the layer 'Reef Basemap'.

• Look for the latitudes in your atlas. Between which latitudes can the majority of the corals be found?

• Name four important regions where corals are located.
  Why do you think the coral reefs are located in these regions and not in Alaska, for example?

• Can you explain why coral reefs are rare or absent in the tropical Atlantic of the west-coast of South America and west-coast of Africa?
  TIP: Study the map of all oceans currents on earth in your atlas and make a link with previous question.

• Look up in your atlas where the Amazon and the Congo River system flow into the ocean. Are there a lot of corals in this region?
  If you think of the difference between ocean water and river water, what can you conclude concerning the appearance of corals?
  Extra: there is another explanation for the absence of corals close to large river mouths. Can you think of one?

• Knowing that corals live in symbiosis with algae, can you explain why most of the corals are localized in shallow areas?

• Because polyps are sessile, oxygen and food have to be brought to the polyps in one way or another. On the other hand, the coral larvae have to be distributed. How do they cope with this problem?

CONCLUSION: After answering the previous questions, can you sum up the limiting physical factors for the occurrence of corals?

TIP: If you don't find the answer, take a look at chapter 1 in the module.