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The Formation of Coral Reefs

Coral reefs are often called the "rainforests of the sea" due to their incredible biodiversity. These underwater structures are built by colonies of tiny animals known as coral polyps. These polyps secrete calcium carbonate to form a hard, protective skeleton. Over thousands of years, the accumulation of these skeletons from countless generations of corals builds up the massive structures we recognize as reefs. Most reef-building corals have a symbiotic relationship with microscopic algae called zooxanthellae, which live within their tissues.

This symbiotic relationship is crucial for the reef's survival. The zooxanthellae perform photosynthesis, converting sunlight into energy. They provide the coral with up to 90 percent of its food and also give the coral its vibrant colors. In return, the coral polyp provides the algae with a protected environment and the compounds they need for photosynthesis. This mutualistic partnership allows coral reefs to thrive in the nutrient-poor tropical waters where they are most commonly found.

Coral reefs require specific conditions to flourish. They need clear, warm, and shallow salt water to allow for adequate sunlight penetration for the algae. Environmental stressors can disrupt the delicate balance of this ecosystem. For instance, a phenomenon known as coral bleaching occurs when rising water temperatures cause corals to expel their zooxanthellae, leaving them white and vulnerable to disease and death. The health of these ecosystems is therefore a sensitive indicator of broader oceanic conditions.