🌐TOEFL Reading 2026

Coral reefs occupy less than one percent of the ocean floor, yet they support roughly a quarter of all marine species. The partnership at the reef's heart is symbiotic: tiny algae called zooxanthellae live inside coral tissues and photosynthesise, passing sugars to the coral while receiving shelter and carbon dioxide in return. This arrangement explains both the reef's productivity and its fragility. When seawater warms by even one or two degrees above the normal summer maximum, corals expel their algae, losing both their colour and their main food source — a stress response called bleaching. A bleached coral is not dead: if temperatures fall quickly, the algae return and the coral recovers. But prolonged bleaching starves the coral, and recovery becomes impossible. Scientists note that reefs under lower pollution and fishing pressure bounce back markedly better, which is why some marine protected areas now restrict both. In the passage, the word 'expel' is closest in meaning to ____.

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