十万个为什么·科学阅读30篇（1）

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珊瑚礁如何在数千年间建造出庞大的结构？

Coral reefs grow slowly as tiny polyps secrete calcium carbonate skeletons that stack up over generations.
Each polyp lives only a few years, but its hard skeleton remains and provides a base for new coral to settle.
Algae living inside coral tissues supply food through photosynthesis, helping corals build skeletons faster.
Ocean temperature, acidity, and sunlight depth all affect how quickly reefs can expand each year.
Storms, predators, and disease sometimes break parts of the reef, but regrowth usually follows within months.
Fossilized reef layers reveal ancient sea levels and climate conditions from millions of years ago.
Modern reefs face threats from warming oceans, which cause corals to expel their colorful algae partners.
Despite covering less than 1% of the ocean floor, reefs support nearly 25% of marine species.
Engineers now copy coral growth patterns to design stronger, self-healing concrete materials.
These underwater cities prove that patience, chemistry, and cooperation can shape entire ecosystems.