Facts We Should Know About Coral Bleaching

Facts We Should Know About Coral Bleaching


What is coral bleaching? 


Coral bleaching is when coral reefs become devoid of colors and turn white – hence the term “bleached.” Although these bleached corals can survive, they are more vulnerable to disease and have a higher mortality rate.


Coral bleaching facts

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Why should we care?

As more corals get bleached, more homes for fish disappear, thus food supply gets reduced. Damaged coral reefs could lead to a compromised ecosystem, which could then affect fish communities, the local communities' livelihood, food supply, and even the production of items that make use of ingredients from the ocean.

  • Coral reefs provide homes and nursery grounds to many fish species. Over one-third of all saltwater fish species live at least part of their lives on coral reefs.
  • Coral bleaching can significantly affect coral mortality, which can then also affect fish communities. This could result to reduced catches for fishermen, which could in turn impact the food supply and other economic factors.
  • Deteriorated coral reefs cannot provide the ecosystem services that local human communities depend on. Bleached coral reefs are less productive and may not be able to sustain the necessary growth rates needed for reefs to provide shoreline protections services.
  • Damaged reefs can also impact reef tourism, as bleached corals obviously have lower aesthetic appeal compared to healthy, live corals. This could result to tourism revenue loss and could in turn threaten the local communities’ livelihood.
  • Did you know that a lot of the medicines and cosmetic products we use today contain ingredients from the ocean? Much of these pharmaceutical compounds are sourced from coral reefs. Unhealthy and bleached coral reefs are less likely to serve as viable sources for these important medical resources.


What causes coral bleaching?

bleached coralsImage Credit

  • Warm water temperatures, which is also one of the effects of the El Niño phenomenon – if the water is too warm, the corals will expel the algae (zooxanthellae) living in their tissues, which then causes the corals to turn completely white (Source).
  • Cold water temperatures can also have the same effect in corals.
  • Other stressors such as human activities, overfishing, increased sedimentation, changes in water chemistry, etc.


To date, coral bleaching has occurred in:

Kanton bleached corals

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  • The Great Barrier Reef – the coast of Australia has recorded bleaching events in 2016, 2006, 2002, 1998, 1994, 1992, 1982, and even 1980. The most widespread and intense of which were in 1998 and 2002, wherein 42% and 54% respectively of reefs were bleached, and around 18% were strongly bleached.
  • Hawaii – major bleaching events were recorded in the island in 2014, 2002, and 1996.
  • Florida Keys – in January 2010, water temperatures in the area dropped to 12.06 degrees Fahrenheit, which is lower than the typical temperatures observed at that time of the year. This resulted in a coral bleaching event and even some coral death.
  • Caribbean – in 2005 the United States lost half of its coral reefs around the northern Antilles near the Virgin Islands and southward of Puerto Rico.
  • Maldives, Sri Lanka, Kenya, Tanzania, and Seychelles – up to 90% of coral reefs were permanently damaged because of warm sea temperatures.


How can we prevent coral bleaching?

  • Minimize your carbon footprint as much as possible, or minimize actions that might aggravate global warming.
  • Participate in tree planting activities. Such activities can help decrease the amount of carbon in the air which contributes to global warming and thus ocean warming.
  • Try to avert overfishing by being more discerning in your seafood choices and purchases – this can be done by using different apps and guides to know which kinds of fish are sustainable to consume.
  • Reduce the use of chemically enhanced fertilizers, pesticides, herbicides, and insecticides – these are non-biodegradable and will most likely end up in rivers and oceans wherein they could then upset the ecosystem.
  • Respect and follow the rules and regulations of any coral reef area you visit. At the same time, use organic or reef-safe sunscreens when you swim in the ocean, including during visits to the beach.
  • As much as possible, do not pollute bodies of water. Avoid dumping chemicals – including human waste, or oils in bodies of water.