View site #952 > ScoreCard for survey #1 > Issue
Introduction | Identification | Impacts | Causes | Actions | More Info
|The Reef Check Survey has a question that may help identify whether mass bleaching is occurring at your site. This question asks what is the percentage of bleached corals. |
The following questions will help to ensure that you have accurately identified mass bleaching as an issue for local reefs.
Have local sea surface temperatures been higher than normal over an extended number of days or weeks? Though the temperature thresholds for corals are highly variable according to their location and species, in some cases even a change of only a few degrees can stress corals to the point of bleaching. See NOAA’s website at: http://www.osdpd.noaa.gov/PSB/EPS/SST/climohot.html for areas where higher than normal sea surface temperatures have been recorded.
Did you observe large areas of dead, white coral? Large areas of dead, white coral, either hard or soft corals, is evidence that mass bleaching may have or is occurring in your area. Small areas of bleached coral, on the hand, may be an indication of other issues affecting local reefs like cyanide fishing, crown-of-thorns starfish (COTS) outbreaks (coral tissue has been removed), or coral diseases.
Did you observe dead coral covered with algae? Dead coral covered with algae may be a sign of an earlier bleaching event or the other stresses mentioned above.
Did you see many standing, live coral that were white? Standing, live coral that is white but with intact tissue and polyps, is another sign that an ongoing bleaching event is occurring. Is it a single coral or a large area that is bleached?
Did you notice giant clams or sea anemones that were dead and/or white? Corals are not the only invertebrates that contain zooxanthellae. Giant clams and sea anemones also house these small organisms within their tissues and environmental stress also affects these animals.
What is the ENSO history? The El Niño Southern Oscillation or ENSO, also known as simply ‘El Niño’ is a phenomenon that results in warmer sea surface temperatures in the tropical Pacific Ocean and can result in climate changes in other parts of the world. ENSO is different from global warming which is a long-term phenomenon that raises sea surface temperatures more or less permanently. If an ENSO event has occurred recently, it may have been the cause of or contributed to local bleaching of corals.
|Shallow reef dominated by Acropora, 80% of which are bleached, August 1995.
Location: Palawan, St. Paul Bay,.Philippines
Photo by: S. Koch
(from ReefBase: http://www.reefbase.org)|