Factors in health and survival of reefs: natural (water temperature, acidity, salinity, algal blooms)
Coral reefs can only survive within very specific natural conditions. Changes in water temperature, acidity, saltiness, or algae levels can damage or kill them.
Real World
During the 2016 mass bleaching event on the Great Barrier Reef, sea surface temperatures just 1°C above average for eight weeks caused zooxanthellae expulsion across 93% of surveyed reefs, turning vast areas white.
Exam Focus
Link each natural stress factor to its specific biological mechanism — e.g., temperature rise → zooxanthellae expelled → bleaching — not just 'coral is damaged'.
Essay Framework
Use PEEL to structure every paragraph. Tap each step for guidance and an example.
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