Stress Corals live in symbiosis with algae Corals release their algae
Freshwater from floods Pollution Disease Sediment Cyanide fishing Many local problems can cause bleaching: Causes of Coral Bleaching
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
Thermal Stress Causes Mass Coral Bleaching
and Mortality Thermal Stress Causes Mass Coral Bleaching and Mortality
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
using satellite sea surface temperature to predict coral bleaching
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 (http://www.comet.ucar.edu/)
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.
Sea Surface Temperature updates available FOR FREE at: coralreefwatch.noaa.gov/satellite
Is today’s temperature above or below average for this location at this time of year? Sea Surface Temperature Anomaly
Bleaching Threshold Temp Maximum monthly mean: Average temperature for the warmest month Bleaching Threshold: 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°
Coral Bleaching HotSpots Is today’s temperature above the average for the warmest month?
Degree Heating Weeks (DHW) How much thermal stress has built up over the past three months?
Degree Heating Weeks (DHW) How much thermal stress has built up over the past three months? Temperature and duration combined: °C – weeks 10 DHWs could be: 1 degree above MMM for 10 weeks 2 degrees above for 5 weeks
Use of DHW to predict coral bleaching DHW = 0 No Thermal Stress DHW >= 4Thermal Stress leading to significant bleaching DHW >= 8Thermal Stress leading to wide spread bleaching and significant mortality
Education Resources Online tutorial –Web pages: how we predict coral bleaching from satellite temperature data –Hands-on exercises –Made for coral reef managers –Also appropriate for high-school students
Education Resources Lesson plans –Focused on satellite technology, coral biology, and coral reef conservation –Fun, hands-on science activities engage students in learning –4th - 6th grade students
Education Resources Lesson plans –Remote Sensing & Electromagnetic Spectrum –Satellite Altimetry –Phytoplankton and Ocean Color –Coral Reefs: Symbiosis and Anatomy –Temperature and Coral Bleaching –Coral Reef Conservation
Education Resources For all of NOAA’s coral reef education resources:
Activity: Using NOAA Satellite Data to Keep Watch on Coral Reefs
Activity Divide the room into four groups: -Bermuda -U.S. Virgin Islands -Puerto Rico -Bahamas Answer questions based on the 2005 Caribbean bleaching event
Activity: Part 1 - SST
Activity: Part 1 - SST
Activity Answer the questions on your handout Work in groups We will come back together to discuss the answers.
Activity: Q & As What were the local conditions at your reef on September 2 nd, 2005? 1.What was the temperature at your reef on that day? B: 28°C; LSI: 30°C; PR: 29°C; USVI: 29°C 2.Was the temperature at your site unusually warm? If so, what was the anomaly? B: +0.75°C; LSI: +0.22°C; PR: +0.75°C; USVI: +1°C 3. Were there doldrums over your reef on that day? Were there doldrum regions close to your reef? B: no; LSI: none over the reef, but yes in the next pixel east; PR: no; USVI: no 4.What was the wind speed in the region around your reef on that day? B: 5-7kt; LSI: 5-7kt; PR: ~ 5kt; USVI: < 5kt
Activity: Q & As How hot was the whole late Summer / early Fall season? 5a.How hot did the water get? B: 28.5°C; LSI: 31°C; PR: 30.5°C; USVI: 30°C 5b.When did the temperature first reach the bleaching threshold? B: mid-August; LSI: late July; PR: mid-August; USVI: early August 5c.How long did the temperature stay at or near the threshold? B: about a month; LSI: 1 month, then a decrease, then another month; PR: 2 months; USVI: 3½ months 6a.When did DHWs start to accumulate at your reef site? B: mid-August; LSI: late July; PR: mid-August; USVI: mid-August 6b.How high did the DHWs get? B: 3 DHW; LSI: 6 DHW; PR: 8 DHW; USVI: 11 DHW 7a.Do you expect that there was coral bleaching at your reef site in 2005? B: maybe; LSI, PR, USVI: yes 7b.If so, how severe do you think the bleaching was? B: mild, if any; LSI: moderate; PR: severe; USVI: very severe
Activity: Q & As How stressed was your reef site compared to other reefs in the Caribbean region? 1. Was the DHW value at your site in the lower third, middle third, or upper third of the range of values experienced in the Caribbean in 2005? B: lowest third; LSI: middle third; PR: middle third; USVI: upper third 2.How did the thermal stress at your site compare to the stress experienced by the other three reefs highlighted in this exercise? B < LSI < PR < USVI 3.How severe do you think the bleaching was at your site compared to the other three reefs? B < LSI = PR < USVI
Activity: How bad was the 2005 Bleaching? Each dot represents the average percentage of the coral colonies that were bleached at that location. > 1500 on-site surveys
Activity: How bad was the 2005 Bleaching? Bleaching surveys within 50 km of four sites used for this exercise Bleaching was worst in the US Virgin Islands Puerto Rico and Bahamas were statistically identical Bermuda < 1% of coral colonies bleached.
Are there signs of hope for bleaching? This reef in Palau was devastated by bleaching in 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 Image from Peter Mumby, University of Exeter
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) 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. 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. Are there signs of hope for bleaching?