Initial Publication Date: August 12, 2008 | Reviewed: May 10, 2019

Lab 6: Using Data to Identify Hot Spots and Predict Bleaching Events

The lab activity described here was created by Erin Bardar and Sarah Hill of TERC for the EarthLabs project.

Summary and Learning Objectives

Under certain environmental stresses, zooxanthellae algae will vacate their coral hosts, leaving corals without their color and, more importantly, their primary food sourcea condition known as coral bleaching. Bleaching can be caused by a number of different stresses, but the primary source of bleaching events is believed to be higher than normal sea surface temperatures. During this lab, students will explore images of bleached and diseased corals, invent a way to model what happens in coral polyps during the process of coral bleaching, and use data products from NOAA's Coral Reef Watch to identify areas around the world where corals are at risk for bleaching.

After completing this investigation, students will be able to:

  • explain how maps of bleaching hot spots and degree-heating weeks help identify reefs at risk for bleaching;
  • describe the consequences of coral reef bleaching; and
  • model the process of coral bleaching in coral polyps.

Open the Student Lab »

Context for Use

This activity follows Lab 5: Trouble in Paradise: Factors That Impact Coral Health, in which students explore various anthropogenic activities that threaten the health and sustainability of coral reefs. Students are now ready to explore one of the most concerning consequences of environmental change that corals facecoral bleaching. It is recommended that students work in pairs or small groups for all three parts of this lab. The entire investigation should take approximately 2 to 3 45-minute class periods. The reading in Part A and, once students are familiar with the Reef Watch data and graphs, the Bleaching Alert data comparisons and questions in Part D can be assigned as homework.

Activity Overview and Teaching Materials

In Part A, students learn about what coral bleaching is and how it affects individual coral polyps and the entire reef community. They search the NOAA Coral Kingdom Photo Gallery to get a visual understanding of how bleached corals compare to healthy corals. They then read about some of the diseases to which weakened corals are susceptible. Students watch two brief videos illustrating coral bleaching and disease. Finally, students use craft supplies to reinvent or extend the coral polyp models they developed in Lab 2, to demonstrate the process of coral bleaching. The following materials are should be available for each group of 3-5 students:

  • craft supplies (i.e., markers, construction paper, glue, etc.)

In Part B, students explore bleaching hot spot data from NOAA's Coral Reef Watch. They first look at the current global hot spot data and then interpret an animation of global hot spot data for the last 3 months to identify regions that are or have been experiencing thermal stress.

In Part C, students explore global degree heating week data to identify regions that are or have been experiencing extended periods of thermal stress and where bleaching is most likely to occur.

In Part D, students apply what they have learned about coral bleaching and interpreting Hot Spot and Degree Heating Week data to evaluate the thermal stress experienced by corals in the Florida Keys and then compare several other global reef sites.

Printable Materials

  • Activity Sheet ( and )

Teaching Notes and Tips

It is recommended that you familiarize yourself with the Coral Reef Watch data products before students work through the exercises in Parts B-D.

If working with older students who are familiar with large data sets and working with spreadsheets, it is possible to download NOAA data used in Part D. See the Extensions section below for more info.


You can assess student understanding of topics addressed in this Investigation by grading their responses to the Stop and Think questions.

State and National Science Teaching Standards


Additional Resources

Background Information

Classroom Extension

  • In Part D, students access biennial reef station data online for multiple sites. If your students are able to work with large data sets and spreadsheets, it is possible to download the NOAA data as txt files. You will need to be knowledgeable about converting to xlsx files or other spreadsheet formats and will probably need to do some cleaning of the data in order to work with it. For example, the four levels of bleaching alerts are in a single column, but by separating into four separate columns, students can graph the four separate alert levels to see the change over time. Students can compare the full time-series graphs they create to the biennial graphs online and consider the benefits and drawbacks of both formats. Cleaned data and sample graph of This is a large file, and may take a few minutes to download depending on your connection.

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