Marine Heatwaves That Are More Common and Intense Put Coral Reef Ecosystems at Risk

Around a billion people depend on coral reefs for their lives because they give them food, draw tourists, and shield coasts from storms.

But more frequent and powerful marine heat waves are endangering these ecosystems.

While prolonged sea temperature increases of merely 1 degree Celsius over the summertime norm can trigger coral bleaching and widespread die-offs, certain reefs appear to be resistant to this thermal threshold.

All about Coral Bleaching

(Photo : Sandy Ravaloniaina/Unsplash)

Changes in temperature, light, or nutrition that stress corals cause them to expel the symbiotic algae dwelling in their tissues, turning them entirely white, as per NOAA.

Coral bleaching may occur as a result of warmer water temperatures.

Corals will eject the algae (zooxanthellae) dwelling in their tissues if the water is too warm, which will turn the coral entirely white.

The term for this is coral bleaching. Coral that bleaches is not already dead. Corals may endure a bleaching episode, although they are more vulnerable to stress and death.

A severe bleaching event in 2005 caused the United States to lose half of its coral reefs in the Caribbean in a single year.

The warm seas that were centered around the northern Antilles, close to the Virgin Islands and Puerto Rico, spread southward.

The 2005 event's thermal stress was higher than the sum of the previous 20 years' worth of satellite data, according to this comparison.

Not every bleaching incident results from warm water.

A coral bleaching event that resulted in partial coral death occurred in the Florida Keys in January 2010 due to the chilly water temperatures.

The dip in water temperature from the normal values for this time of year was -6.7 degrees Celsius, or 12.06 degrees F.

Also Read: Corals That Experience Heat Stress are More Likely to Tolerate High Water Temperatures

Red Sea reefs in the north withstand bleaching in warming waters

Corals in the Red Sea are estimated to have developed a high tolerance to heat some 7,000 years ago after overcoming a thermal barrier of 32 degrees Celsius at the southern sea's entrance.

Corals that couldn't handle the heat, on the other hand, were filtered out, as per Phys.Org.

Red Sea corals may now withstand heat stress up to 32 degrees Celsius because of their evolutionary memory, albeit this is difficult to verify without reliable data on bleaching.

The researchers gathered information on coral bleaching for the last 20 years along the Egyptian coast using the citizen science tool Reef Check.

This was compared to remotely detected sea surface temperatures from the previous 40 years, which supported the finding that bleaching in the Red Sea usually takes place at 32 degrees Celsius.

Corals in the northern Red Sea, where temperatures range from 25 to 28 degrees Celsius, have not undergone mass bleaching, in contrast to corals in the center and southern Red Sea, where temperatures are currently 30 to 32 degrees Celsius.

Using several scenarios of greenhouse gas emission, the researchers employed global climate models to forecast future Red Sea temperatures.

By 2100, the northern region would have warmed 2.5 degrees Celsius under the worst-case scenario.

To save these reefs of future promise, conservation measures must be a priority.

The advantageous genetic and physiological features that have persisted for 7,000 years should then be discovered, experts hoped.

Related Article: Coral-Algal Symbiosis May Help in Recovery from Coral Bleaching Due to Climate Change and Ocean Warming