Teachers

Key Concept 
Coral reef bleaching occurs when water temperatures exceed the maximum range that corals can tolerate.  Corals typically grow in warm tropical waters between 70-85 degrees Fahrenheit. When sea surface temperatures rise above this level or other stresses occur, the corals expel the symbiotic algae that gives them color.

This is an inquiry-based lesson using data from the NOAA/NESDIS website. The lesson will help students understand the causes of coral reef bleaching using current satellite data.

Background Scenario
There are many species of coral that grow throughout the world’s oceans, but most corals have common structural characteristics.  Corals have been in existence for nearly 200 million years but reached their current level of diversity only 50 million years ago.  There are two main types of corals; hard corals composed of stony calcium carbonate and soft corals made up of a protein/calcium carbonate material.  Scleractinians, or hard corals, have rigid exoskeletons called corallites that protect the soft, delicate bodies. Some examples of scleractinians are the brain, star, staghorn, elkhorn and pillar corals. Gorgonians, or soft corals, lack an exoskeleton and sway with currents. Some examples of goronians are sea fans, sea whips, and sea rods. 

A coral contains a very thin outer layer of living coral polyps. A polyp is a hollow, cylindrical animal with a mouth that is surrounded by tentacles, armed with stinging cells, for capturing food.  Each coral polyp excretes a calcereous exoskeleton. Under the polyps is the dead coral skeleton composed of calcium carbonate. in its tissue the polyp hosts an algae called zooxanthallae that gives coral its green, blue, purple or brown color. When corals become stressed, usually when sea surface temperatures are too hot or too cold, many coral polyps expel their zooxanthallae. The polyps of the coral then lose their pigmentation and appear nearly transparent on the white skeleton. This phenomenon is referred to as coral bleaching.

Prior to the 1980’s, most bleaching events were attributed to localized phenomena such as major storms, severe tidal exposures, sedimentation, rapid salinity changes, pollution, or thermal shock.  Since 1980, research has shown a direct relationship between bleaching and water temperature stress.  Extreme water temperatures have been implicated in the majority of the major bleaching events of the 1980s and 1990s.

Goals
The student will:

• Identify questions and concepts that guide scientific investigations.
• Design and conduct scientific investigations.
• Use technology to improve investigations and communications.
• Understand the interdependence of organisms.
• Understand the diversity and adaptations of organisms.
  

Science Process Skills
Observing, inquiring, predicting, communicating, organizing, graphing, relating, interpreting

Concept Connections
ecosystems and populations, organisms, energy flows, scientific inquiry

Vocabulary
Polyps, zooxanthellae, scleractinian, gorgonian, symbiotic, phytoplankton, corrallites, El Niño, La Niña

Materials
Computer, Internet Access, pen or pencil

Grade Level: grades 9-12

Key Question: If the world’s oceans are warming, how will these rising temperatures affect our ocean’s coral reefs?

Teacher Preparation
Begin the lesson by asking the Key Question. The students’ answers will help you become familiar with their knowledge of coral reefs. The PowerPoint presentation is provided to give the students the necessary background information to complete this lesson.

Begin the inquiry by generating student questions relating to the coral reef bleaching and sea surface temperatures data provided in the PowerPoint presentation.  As the students generate questions, record those questions on the board.

Once the students have all the necessary background information, you may begin asking them the "Active Inquiry Questions". Guide the students with this series of questions, provided on the student page, to get them started on the inquiry part of the lesson. These questions are designed to guide your students through their study of the coral reef data. Their inquiries and subsequent findings will lead them to more complex questions that they can record for further investigation. Your goal is to help the students generate questions that can later be used in a hypothesis for research. Also available is a Guidelines for a Good Research Question link. This link will help students become familiar with the process of creating a good scientific question that can be answered using the data provided by the NOAA/NESDIS website.

Once the students have generated enough questions, split them up into groups of three or four. Each group is assigned a different question to investigate. Lead each group through the Researching a Hypothesis link to help guide them in researching a hypothesis. It should take a 90-minute class period to provide background, generate questions, look at data, assign groups, and go over methodology. The following day, the students can use the class time to investigate their hypotheses and present their results. It is important that you not feel like you have to have all the answers. Remember this is inquiry – let the students teach you!

Active Inquiry Questions 
Here are a few examples the teacher can give the students to get them started. Following each question is a link to data that will help answer the question. All external links open in a new window. The maps below show experimental NOAA/NESDIS data and should be interpreted with caution.

1. Where do you think most coral reefs are located?
   Why do you think they are located there?
   What do you think causes coral reef bleaching? Why?
   Are there any other factors that could contribute to this problem? If so, what are they?
   
   The Coral Reef Bleaching information page on the NOAA/NESDIS web page.
   http://www.coris.noaa.gov/
   
   
2. Are there any regions of the US where you think you might find coral reef bleaching? Why or why not?
   
   The links below are to Sea Surface Temperature Maps.
   Visit the link "How to Read A Sea Surface Temperature Map" before trying to answer the questions.
   
   World SST http://www.osdpd.noaa.gov/PSB/EPS/SST/data/FS_km5000.gif
   
   U.S. East Coast SST http://www.osdpd.noaa.gov/PSB/EPS/SST/data/FS_km50f100.gif
   
   U.S. West Coast SST http://www.osdpd.noaa.gov/PSB/EPS/SST/data/FS_km50f200.gif
   
   Alaska & Hawaii SST http://www.osdpd.noaa.gov/PSB/EPS/SST/data/FS_km50f300.gif
   
   
3. Do you think that the time of year has anything to do with coral reef bleaching events?
   If so, what months do you think would have the greater likelihood of coral reef bleaching? Why?
   
   This link is a list of Monthly Sea Surface Temperature Anomaly Charts. Use different months of data to compare the seasons. http://www.osdpd.noaa.gov/PSB/EPS/SST/climo.html
   
   
4. Do you think El Niño/La Niña have an effect on coral reef bleaching?
   If you are unsure about what El Niño/La Niña are use this link to help you find out more.
   
   El Niño Theme Page.http://www.pmel.noaa.gov/toga-tao/el-nino/nino-home.html
   
   
5. You are a scientist who is interested in monitoring the health of Indian Ocean coral reefs. You are planning two, 30-day expeditions with other scientists to collect the necessary data. Based on the 1998 Sea Surface Temperature data and significant coral reef bleaching events, during which months of the year would plan your research expeditions?
   
   1998 Indian Ocean Data - http://www.osdpd.noaa.gov/PSB/EPS/SST/retro.html

After the students have looked at some of the data listed above, have them look at the time sequence of Indian Ocean Bleaching events. This might help the students to generate even more questions.