Summary
Biodiverse ecosystems built by coral polyps living in partnership with symbiotic algae.
In depth
Reefs form in warm (above 18 °C), clear, shallow water with zooxanthellae providing up to 90 percent of the coral's energy. Types: fringing, barrier and atolls. They protect coasts and support fisheries.
Corals are cnidarians building calcium carbonate skeletons. Reef growth is a balance between calcification and erosion. Reefs face warming, acidification and pollution.
Key idea: reefs are biodiversity hotspots built by animals.
Coral reefs are built by colonial polyps that secrete calcium carbonate skeletons, over centuries forming massive limestone structures. Reef-building (hermatypic) corals harbour symbiotic dinoflagellates (zooxanthellae) that provide up to 90 percent of the coral's energy through photosynthesis, while the coral gives shelter and nutrients.
Reefs cover less than 1 percent of the seafloor but support about 25 percent of marine species. They protect coasts from waves, support fisheries and tourism, and need clear, warm (23 to 29 °C), shallow, well-lit water. Types are fringing, barrier and atoll, as Darwin explained.
Example: the Great Barrier Reef extends about 2,300 km.
Frequently asked questions
What is Coral Reefs?
Biodiverse ecosystems built by coral polyps living in partnership with symbiotic algae.
Which area of biology covers Coral Reefs, and how advanced is it?
Coral Reefs is one of the 54 topics in Marine & Environmental Biology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Coral Bleaching, Blue Carbon, Kelp Forest Ecology.
Why does Coral Reefs matter?
Reefs are among the most threatened ecosystems.
Can you give an example of Coral Reefs?
The Great Barrier Reef is about 2,300 km long.
What should I learn before Coral Reefs?
Coral Reefs is a Beginner topic, so no earlier topic is required. Other Beginner topics in Marine & Environmental Biology that pair well with it include Oceans, Ocean Zones, Plankton.
What topics are related to Coral Reefs?
The closest topics to Coral Reefs are Coral Bleaching, Blue Carbon, Kelp Forest Ecology, Ocean Acidification. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Coral Reefs?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Coral Reefs. To practise the whole of Marine & Environmental Biology, use the Marine & Environmental Biology quiz.
How is Coral Reefs different from Coral Bleaching?
Coral Reefs: Biodiverse ecosystems built by coral polyps living in partnership with symbiotic algae. Coral Bleaching: Heat stress causes corals to expel their symbiotic algae, turning white and risking death. Read both side by side and note what each one explains.
How should I study Coral Reefs step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Coral Bleaching and explain the difference aloud. Finally, take the Marine & Environmental Biology quiz and come back to this page for any question you miss.