How does ocean temperature relate to coral bleaching?

The relationship between ocean temperature and coral bleaching is fundamentally tied to the stress response of corals to higher temperatures. When water temperatures rise beyond the normal range, corals become stressed, which triggers them to expel the symbiotic algae known as zooxanthellae that live within their tissues. These algae provide essential nutrients to the corals through photosynthesis and also contribute to their vibrant colors.

When the corals expel these algae, they lose not only their primary source of nutrition but also the pigments that give them their beautiful colors, resulting in a phenomenon known as bleaching. Without the algae, the corals appear white, and their health declines significantly. Sustained high temperatures can lead to widespread coral mortality, severely impacting marine ecosystems and the biodiversity they support.

The other choices do not accurately depict the effects of temperature on coral health. While it is true that optimal temperatures can support coral growth, extreme heat is harmful, leading instead to bleaching. Additionally, temperature does play a significant role in coral health, contrary to the wrong assertion that it has no effect. The idea that lower temperatures somehow enhances the color of corals also misrepresents the impact of temperature on these vital marine organisms.