Coral Reefs 101 | National Geographic

Summary

Coral reefs, despite their plant-like appearance, are complex colonies of tiny animals called polyps. These invertebrates build limestone skeletons, forming vast underwater structures that support 25% of marine life, including an estimated two million species. Corals derive much of their color and sustenance from symbiotic algae. However, climate change threatens these ecosystems with warming waters causing coral bleaching, endangering not only the reefs but also the millions reliant on them for food and habitat.

Takeaways

• 🌊 Coral reefs are vibrant underwater ecosystems found in tropical oceans worldwide.
• 🐙 Despite their plant-like appearance, corals are actually tiny animals known as polyps.
• 🏔 Polyps secrete limestone skeletons for protection and support, contributing to the formation of reefs.
• 🌱 Coral polyps form colonies that function as a single organism and can grow into massive structures over time.
• 🏞️ The Great Barrier Reef in Australia is the largest coral reef system, beginning to form around 20,000 years ago.
• 🐠 Coral reefs host 25% of all marine life, supporting an estimated two million species, despite covering less than 1% of the ocean floor.
• 🌈 Corals are translucent, and their vibrant colors come from symbiotic algae called zooxanthellae living within their tissues.
• 🌡️ Stress from pollution or other factors can lead to coral bleaching, where corals expel their algae and their white skeletons become visible.
• 🔬 Coral skeletons form layers that record historical ocean conditions, providing a climate record for scientists to study.
• ⚠️ Climate change poses a significant threat to coral reefs, potentially leading to their widespread loss by the end of the century if not addressed.

Q & A

What are coral reefs and where can they be found?

Coral reefs are vibrant underwater ecosystems made up of tiny animals called polyps. They can be found in tropical ocean waters around the globe.

What is the size range of coral polyps?

Coral polyps can range from the size of a pinhead to a bit larger than a basketball.

How do coral polyps protect themselves and provide support?

To protect their soft bodies and add support, polyps secrete limestone skeletons, also known as calicles.

What is the significance of coral colonies?

Polyp calicles connect to create a colony that acts as a single organism. Over time, these colonies grow and join with others to form extensive reefs.

How large is the largest coral reef and where is it located?

The largest coral reef is Australia's Great Barrier Reef, which began growing about 20,000 years ago.

What percentage of marine creatures live in coral reefs?

Despite covering less than 1% of the ocean floor, coral reefs are home to 25% of all marine creatures.

How does the biodiversity of coral reefs compare to rainforests?

Coral reefs are estimated to host up to two million species, rivaling the biodiversity of rainforests.

What role do coral reefs play in the growth of young fish?

Coral reefs provide a rich habitat that helps protect young fish as they grow.

How do coral reefs get their vibrant colors?

Coral reefs get their rainbow of colors from algae, or zooxanthellae, that live in their tissue.

What is coral bleaching and what causes it?

Coral bleaching occurs when corals become stressed by pollution or other factors, causing them to evict their algae and revealing their white skeletons.

How do coral reefs provide a window to the past?

As coral grow, their limestone skeletons form layers that vary in composition and thickness based on ocean conditions at the time, allowing scientists to study past climates.

What threat does climate change pose to coral reefs?

Climate change, particularly warming waters, results in prolonged coral bleaching that can kill coral reefs or leave them vulnerable to other threats.