1. 8:29 REEF HABITATS
Coral reefs are only found on western boundary currents where water is warm, shallow, and clear with good light.
The coral reef is able to exist in these POOR conditions because of complex symbiotic relationships.
It is an “oasis” in the biological desert of tropical waters. The explosion of life in reefs are an exception not the rule.

2. REEF ZONES
1. outer slope - good coral growth
2. buttress zone - heavy pounding
of waves smashes all but the densest coral
3. algae ridge - coralline algae withstands wave pounding
4. reef flat - often exposed at low tide, good coral variety
5. leeward islands - densest coral due to lack of waves

3. There are different types of coral reefs:
Fringing reef - borders the coastlines
ex: Florida Keys
2. Barrier reef - steep, sloped reef separated from the shore or island by a lagoon or channel
ex: Great Barrier Reef miles long

4. 3. Atoll - circular ring of reef surrounding a lagoon
ex: many in Pacific and Caribbean
Darwin proposed that the 3 types of reefs are simply stages in the aging or evolution of reefs.
Recent core samples show that reefs do not always form in this pattern.
Daly’s theory explains the formation of reefs as the result of changes in sea level during the ice age.

5. Natural walkway in Maldives

6. Adaptations:
Versatility, symbiosis and a variety of niches help reef organisms respond to an unproductive environment.
Reefs have no plants. Primary productivity is provided by the zooxanthellae, a dinoflagellate algae that has developed a mutualistic symbiosis within the coral animal.

7. Corals provide protection for the algae.
Coral waste products (carbon dioxide, nitrates and phosphate) supply materials for photosynthesis.
In return, the algae supplies the food and aids in calcium carbonate secretion of the coral skeleton.

8. Competition is intense for space, light and nutrients
Competition is intense for space, light and nutrients. Habitat stratification around the fore reef, flats, forward wall and back reef provide for a variety of populations.
Reef fish are brightly colored to identify and attract mates.
Sex-changes are common among reef fish to provide enough mating couples.
Many are camouflaged to blend in with sponges and sea fans. Some are poisonous and are very aggressive.

9. The nocturnal - diurnal patterns, and natural disasters such as hurricanes also help reduce overcrowding.
Some animals, like the crown-of-thorn starfish, parrotfish, cowries and bristleworms, eat coral and pass it through their bodies to form sand.
The process is called bioerosion - erosion is caused by living organisms.

10. Comparison of Polar and Tropical Seas