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| Read each sentence and identify the word/phrase that you believe correctly completes the statement. Then, click on the arrow to see if your answer is correct. 1. The most important reef architects are the corals, which deposit skeletons made of . Most corals are colonies of many individual . 2. Reef-building corals contain symbiotic that provide and enable the coral to rapidly build its . 3. algae help reef growth by depositing , by resisting erosion by , and by cementing together coarse . 4. Coral reefs need and , clear water, so they are found only in the . Corals are very sensitive to , fresh water, and of many kinds. 5. The main types of reefs are , , and . 6. When a island slowly sinks, leaving only living, growing reef near the surface, an is formed. 7. Though the surrounding water is poor in , coral reefs have high production. This is because in reef communities nutrients are , nitrogen is , and the few nutrients that are brought in are used efficiently. 8. Seaweeds are important primary on coral reefs, even though they are kept in check by limitation and grazing. 9. Sessile reef organisms must often compete for . Among the most important competitors are corals, , , and . 10. The sea star has undergone population explosions on many reefs in the . This may be due to natural or human factors. 11. Among the most important grazers on reefs are , , and microherbivores. Grazers are important because they prevent from dominating slow-growing organisms. |