Identity card of a coral reef
-	Global distribution of coral reefs –
-	What do corals need ? – 

To localize the areas where corals occur, open the following site: 
https://catalogue.odis.org/view/612
Go to ‘Maps – Localization 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 4 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 one way or another. On the other hand, the coral larvae have to be distributed. How do they cope with this problem?
___________________________________________________________
___________________________________________________________

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