1. Using NOAA Satellite Data to Keep Watch on Coral Reefs
PDF files for this presentation, more data activities (and the answer sheet!) are found on our website:
Modified by Kristine Grayson, University of Richmond

2. Corals live in symbiosis with algae
Stress
Corals release their
algae
For more on coral bleaching:
Also see this great video:

3. Causes of Coral Bleaching
Many local problems can cause bleaching:
Freshwater from floods Pollution Disease Sediment Cyanide fishing

4. Temperature When the water gets hot and stays hot, corals will bleach
Causes of Coral Bleaching
But only one thing causes bleaching at a Regional or Global scale
Temperature When the water gets hot and stays hot, corals will bleach

5. Thermal Stress Causes Mass Coral Bleaching
Geographically widespread coral bleaching was first reported from the SE Tropical Pacific
Since then several major coral bleaching events have occurred in 1987/88, 1990/91, 1994/95, 1997/98, 2001/02, 2005…
Coral bleaching has been reported from all of the tropical seas and some areas have bleached repeatedly.
Now recognised as one of the most significant global threat to coral reefs
Coral bleaching does not discriminate between ‘pristine’ and impacted area

6. Thermal Stress Causes Mass Coral Bleaching

7. Thermal Stress Causes Mass Coral Bleaching
and Mortality

8. What are the consequences?
Environmental impacts
Loss of coral
Changes in reef community
Loss of biodiversity
Economic impacts
Decreased tourism appeal
Fishery decline
Loss of ecosystem “services”
Subsistence fishing
Recreation
Cultural significance
Shoreline protection

9. Using Satellite Sea Surface Temperature to Predict Coral Bleaching
Have students go here and explore

10. What satellites do we use?
NOAA’s polar-orbiting POES satellites view most of the earth’s surface every day.
Animation from the COMET Program (

11. How do we measure the temperature of the ocean from 850km above the surface?
If you stand next to a fire, you can feel the heat on your skin.
Satellite uses this infrared radiation to “feel” how warm the ocean is.

12. Sea Surface Temperature Anomaly
Put today’s map here!
This is an example of the global SST anomaly product from Coral Reef Watch. Blue to purple colors mean that the current SST is below the long-term average for that day and in that location; yellow to red means the SST is above average.
Click SST
Is today’s temperature above or below average
for this location at this time of year?

13. Bleaching Threshold Temp
Maximum monthly mean:
Average temperature for the warmest month
Bleaching Threshold (Defines a Hot Spot):
One degree above Maximum Monthly Mean
(MMM + 1°C)
Varies with latitude and local conditions:
Gulf of Oman: 33.5°
Florida Keys: 30.3°
Oahu, Hawaii: 28.0°
Galapagos: 27.5°
The concept for a bleaching threshold temperature was introduced in 1990 as one degree above the summertime maximum temperature. Coral Reef Watch define the summertime maximum temperature as being the maximum of the monthly mean temperatures.

14. Is today’s temperature above the average
Coral Bleaching HotSpots
Put today’s map here!
An example of a HotSpot chart. Areas in white indicate that the current SST is below the MMM. Areas in the shades of purple are above MMM, but still less than one. Any areas in orange to red are above the bleaching threshold temperature, defined as MMM + 1.
More info:
Is today’s temperature above the average
for the warmest month?

15. Degree Heating Weeks (DHW)
Put today’s map here!
An example of the Degree Heating Week chart. The units are “°C-weeks”, combining temperature and time into one measure of thermal stress.
How much thermal stress has built up
over the past three months?

16. Degree Heating Weeks (DHW)
Temperature and duration combined: °C – weeks
10 DHWs could be:
1 degree above MMM for 10 weeks
2 degrees above for 5 weeks
0.5 degrees above for 20 weeks
How much thermal stress has built up
over the past three months?

17. Use of DHW to predict coral bleaching
DHW = 0 No Thermal Stress
DHW >= 4 Thermal Stress leading
to significant bleaching
DHW >= 8 Thermal Stress leading
to wide spread bleaching
and significant mortality
Accumulated thermal stress, represented by the Degree Heating Weeks product, is the best indication of coral bleaching risk. If DHWs are zero, there has been no thermal stress in the region over the last 3 months. If DHWs rise above 4, the area is likely to see significant coral bleaching. DHWs above 8 can cause widespread bleaching, and some coral mortality may occur.

18. Coral Bleaching Alerts
What areas are currently vulnerable?

19. Examine the Data Divide into four groups: Bermuda U.S. Virgin Islands
Puerto Rico
Bahamas
Examine temperatures leading up to the 2005 Caribbean bleaching event

20. Long-term Temp Trends

21. Implications Today

22. SST  Hotspots  DHW
STOP HERE TO DO MODULE

23. NOAA Product

24. How bad was the 2005 Bleaching?
These data come from local researchers throughout the Caribbean and Guld of Mexico region. Remember that this is not based on satellite data now– these are researchers actually swimming around on the reef and measuring how much of the coral bleached.

25. How bad was the 2005 Bleaching?
> 1500 on-site surveys
These data come from local researchers throughout the Caribbean and Guld of Mexico region. Remember that this is not based on satellite data now– these are researchers actually swimming around on the reef and measuring how much of the coral bleached.
Each dot represents the average percentage of the coral colonies that were bleached at that location.

26. How bad was the 2005 Bleaching?

27. How bad was the 2005 Bleaching?
Bleaching surveys from the four sites

28. How bad was the 2005 Bleaching?
Bleaching surveys from the four sites
Bleaching was worst in the US Virgin Islands
Puerto Rico and Lee Stocking Island were statistically identical
Bermuda < 1% of coral colonies bleached.

29. Are there signs of hope for bleaching?
This reef in Palau was devastated by bleaching in 1998.
Ten years later, the reef is covered with healthy corals.
If conditions are favorable, reefs can recover:
good water quality
low fishing pressure
many grazing fish
low nutrient pollution
Coral bleaching can be a depressing topic to think about, especially when we talk about climate change. These slides give some signs of hope, and explain why we don’t give up on coral reefs altogether.
Image from Peter Mumby, University of Exeter
(more at

30. Are there signs of hope for bleaching?
Local managers can:
Reduce bleaching
Reduce light stress
Cool reefs, increase mixing
Increase survival
Improve water quality
Reduce disease prevalence
Aid recovery
Coral fragmentation
Encourage recruitment
Protect ecosystem functions (herbivory)

31. Are there signs of hope for bleaching?
After bleaching and death of corals….
Sensitive coral species are killed….
The corals that remain are the ones that can tolerate higher temperatures.
Result? Less diversity, but the reef as a whole develops bleaching resistance.

32. Are there signs of hope for bleaching?
Some places are heating more slowly than others
These regions may act as natural refuges where coral reefs may survive.
A recent article on this topic:
Kleypas, J. A., G. Danabasoglu, and J. M. Lough Potential role of the ocean thermostat in determining regional differences in coral reef bleaching events
Geophysical Research Letters, vol. 35
9 February 2008