How Do Corals Build Reefs?

Duration: 2.5 minutes
Grade Level: Appropriate for all ages; content connects to NGSS standards for grades 5 and above

Let's look inside a polyp to see how it helps build a reef. It takes carbon from algae and seawater, turns it into calcium carbonate, and uses this chalky substance to build an internal skeleton.

This visualization showing the interior of the polyp during the skeleton-building process will change your understanding of how hard corals construct entire reefs!

You can download the still images below to use when teaching how corals build reefs—just right click and 'Save Image As'.

Get up close and personal views of corals that you can't even get underwater!  Look at corals from all angles with these free 3D models created by The Hydrous.  These models are accurate representations of living corals, made by stitching together 2-dimensional photographs collected by snorkelers and SCUBA divers.

Two of the biggest challenges to truly understanding how corals live are the minuscule size of individual coral polyps and their painfully slow rate of growth and reproduction. To overcome these challenges, coral reef ecologists and technologists have developed tools that allow them to see corals at an unprecedented scale and pace. Armed with a suite of underwater time-lapse microscopes, ecologists can now peer into the secret lives of coral polyps and study how these tiny organisms grow, reproduce, construct their calcium carbonate homes, and interact with their symbiotic algae.

While this video doesn't necessarily cover the following standards in depth, it is a compelling resource you can use to supplement your curriculum that does.

Disciplinary Core Ideas

• 5-ESS2-1 Do you think coral reefs are a part of the geosphere or the hydrosphere, and why? How do coral reefs as solid structures influence the living system or landform shape around them?
• MS-LS2-4 How does ocean acidification affect populations within the coral reef ecosystem?

Crosscutting Concepts

• Structure and Function