IVA 21. Monitoring Coral Bleaching Background Because coral bleaching results from many environmental factors, defining the causes of bleaching is important for conservation of reefs. Recording the extent of the bleaching and what environmental factors were present at the particular coral reef at a given time is one of the first steps to establishing a direct link between an environmental factor (such as global warming) and coral reef health. Further background on coral bleaching can be found in the Introduction to Coral Reefs (IVA Introduction to Coral Reefs ) document in this curriculum. C e P Focus Question How can the causes of coral bleaching be identified? Learning Objectives Students will describe monitoring that could be used to determine the cause or causes of coral bleaching. Materials Picture of coral reef included here Ruler with cm markings Introduction to Coral Reefs (IVA Introduction to Coral Reefs) reading from this curriculum Student work sheet Teaching Time 45 minutes W Procedure 1. Assign students to read the document Introduction to Coral Reefs and distribute copies of the student work sheet Coral Bleaching in the Great Barrier Reef. Direct students to examine the photo. 2. Lead the students in a discussion of the factors that are thought to cause coral bleaching and therefore must be measured to determine the cause of bleaching. These factors include Elevated seawater temperatures Increased levels of ultraviolet irradiation Turbidity Chemical pollutants Coral diseases
3. Assign students the problem of designing an appropriate monitoring protocol to study coral bleaching and its causes. First they will need to determine the extent of the problem in their study area by confirming if the bleaching is spreading or shrinking and identifying the factors in the study area that are known to cause bleaching. Challenge students to develop as many ideas as possible and to list the methods they will use to gather measurements needed to answer the questions. Let the students develop their own ideas for approaches to monitoring coral bleaching, then guide them with the suggestions given below. They should consider the following: Selection of an appropriate study site, a representative reef that is characteristic of the area Choice of methods or approaches to studying coral bleaching. These methods could include photography (analysis of photos of the study area taken at set intervals of time, monthly, every six months, etc.) and direct measurement (using quadrats to estimate the amount of bleaching in a selected area of the reef at specified intervals) Appropriate sampling frequency: should the reef be examined weekly, monthly, biannually, yearly? Sampling must be consistent. Discuss the need for consistent data collection techniques over time to determine extent of bleaching as well as environmental parameters Calculate the extent of bleaching, and compare to environmental stresses known to be occurring in the area. This information is needed in order to determine the cause(s) of the bleaching. Some of these stresses could be: s Pollution water testing will be needed s Coral diseases observations for disease diagnosis s Water turbidity water clarity measurements s Warming water temperature measurements Consistent periodic measurements are needed for all of the above to determine the cause(s) of coral bleaching. To establish if the problem is localized or more widespread, the sampling must be duplicated at different locations. 4. Have the students complete the activity outlined on the student work sheet.
Coral Bleaching on the Great Barrier Reef, Australia. Monitoring Coral Bleaching Student Work Sheet Bleached corals are white. Photo: Great Barrier Reef Authority? 1. What parameters should be measured to identify the cause of coral bleaching? 1. 2. 3. 4. 5. 2. How will you know if bleaching in your study area is getting worse? Develop a sampling plan to determine if bleaching is spreading. Consider the following: Selection of sampling site How often to sample Methods to measure bleaching
3. Using the photograph above, estimate the amount of area of bleached coral in square centimeters. Measure a selected area that is bleached and estimate the percent of the reef that has been damaged by coral bleaching. 4. Would photography be a dependable method of measurement if you had access to aerial views of the reef?
Monitoring Coral Bleaching Teacher Answer Key 1. What parameters should be measured to identify the cause of coral bleaching? 1. Seawater temperatures 2. Levels of ultraviolet irradiation 3. Turbidity 4. Chemical pollutants 5. Coral diseases 2. How will you know if bleaching in your study area is getting worse? Develop a sampling plan to determine if bleaching is spreading. Consider the following: Selection of sampling site: Choose a reef that is representative of reefs in the area. If you are trying to determine whether bleaching is localized or more widespread, you must set up sampling sites throughout the tropics. This is an important consideration if trying to determine if climate change is the cause of bleaching. How often to sample: Consistent periodic sampling is needed, whether weekly, monthly, biannually, or yearly. Students should remember that more frequent sampling is usually more expensive and may not be necessary to capture the variability or trends in their reef area. Methods to measure bleaching: Photography of sample area or use of quadrants and direct measurement of area of damaged coral to measure extent of bleaching. Various methods to measure causative parameters. 3. Using the photograph above, estimate the amount of area of bleached coral in square centimeters. Measure a selected area that is bleached and estimate the percent of the reef that has been damaged by coral bleaching. About 50 percent 4. Would photography be a dependable method of measurement if you had access to aerial views of the reef? This method is useful if the site and angle of the photographs are carefully chosen to be consistent from photo to photo.
o References and Further Reading 2003 Reef Futures: Cooperative Research Centre for the Great Barrier Reef World Heritage Area. http://www.reeffutures.org/topics/bleach/biology.cfm. Accessed July 2006. NOVA: Coral Bleaching: Will Global Warming Kill the Reefs? http://www.science.org.au/nova/076/ 076key.htm. Accessed July 2006.