1.   The critical point is the effect of depth on illumination, which affects the photosynthetic activity of symbiotic algae.

2.   Bleaching occurs when hot water prompts corals to expel their symbiotic algae.

3.   A reef becomes bleached when its symbiotic algae die because of warmer water temperatures or some other environmental shock.

4.   This occurs when the symbiotic algae that lives within the coral are expelled, leaving the white of the coral shells as the dominant color.

5.   When corals are stressed by high temperatures or other environmental conditions, they expel the symbiotic algae that are the source of most of their food.

6.   Increased turbidity reduces the penetration of sunlight, thus inhibiting photosynthesis in primary producers such as the symbiotic algae of coral polyps.