ENVIRONMENT

Scientists are warning that devastating bleaching of colorful coral is becoming a worldwide crisis. (Christian Science Monitor)

Use our resources to learn more about coral reefs and the threats they face.

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit.

Discussion Ideas

• Scientists have announced the emergence of a major worldwide coral bleaching event. What is coral bleaching? Read through our article and take a look at NOAA’s terrific graphic above for some help.
  • Coral bleaching describes the process of corals being stripped of their protective algae. Algae are what give corals their bright colors, so animals that lack algae partners look white and “bleached.”

• Does coral bleaching kill corals?
  • No. Bleaching does make coral less healthy, however, for two main reasons.
    • Bleaching causes corals to lose a major source of nutrients (algae).
    • Corals are more susceptible to disease without their protective algae partners.
  • According to NOAA, corals can survive a bleaching event if water temperatures return to normal quickly.

• What major factors contribute to coral bleaching?
  • A change in ocean temperature is the major reason for coral bleaching events.
    • Warming. Most coral bleaching is associated with warming waters. “In 2005,” for instance, “the U.S. lost half of its coral reefs in the Caribbean in one year due to a massive bleaching event. The warm waters centered around the northern Antilles near the Virgin Islands and Puerto Rico expanded southward. Comparison of satellite data from the previous 20 years confirmed that thermal stress from the 2005 event was greater than the previous 20 years combined.”
    • Cooling. Not all bleaching events are due to warm water, NOAA reminds us. “In January 2010, cold water temperatures in the Florida Keys caused a coral bleaching event that resulted in some coral death. Water temperatures dropped 12.06° Fahrenheit lower than the typical temperatures observed at this time of year. Researchers will evaluate if this cold-stress event will make corals more susceptible to disease in the same way that warmer waters impact corals.”
  • Runoff and pollution, overexposure to sunlight, and extreme low tides can also contribute to coral bleaching.

• According to NOAA, we are experiencing the third recorded coral bleaching event. When were the previous two? Do the coral bleaching events have anything in common?
  • Previous coral bleaching events took place in 1997-1998 and 2009-2010.
  • All three major coral bleaching events took place during El Niño years. El Niño is a predictable climate pattern that causes unusually warm currents in the Pacific. (Learn more about El Niño here.)

• One scientist quoted in the Christian Science Monitor article describes bleached coral as “covered with scuzzy algae.” Wait a minute—I thought coral bleaching involved corals losing their algae?
  • Different algae! There are more than 70,000 species of algae, but the perfect match for corals belong to the group called zooxanthellae.
    • extra credit! Zooxanthellae are part of the big, beautiful SAR group in this ‘circle of life,’ and mostly traceable to the Symbiodinium genus here.

TEACHERS’ TOOLKIT

Christian Science Monitor: Major coral bleaching crisis spreads worldwide

Nat Geo: Coral Reefs: An Ocean of Trouble

NOAA: What is coral bleaching?

NOAA: Zooxanthellae… What’s That?

(extra credit!) NOAA: NOAA declares third ever global coral bleaching event