Coral bleaching occurs when coral polyps expel algae that live inside their tissues. Normally, coral polyps live in an endosymbiotic relationship with these algae, which are crucial for the health of the coral and the reef. The algae provides up to 90 percent of the coral's energy. hen water is too warm, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white. This is called coral bleaching. When a coral bleaches, it is not dead. Corals can survive a bleaching event, but they are under more stress and are subject to mortality.

1. Erica Weston

2. The Importance of Coral Reefs
 Coral reefs are like the
rainforests of the sea
 Biologically diverse
 Support 33% of marine
fish species
 Provides medicines,
chemicals, and other
resources .

3. The Importance of Coral Reefs
 Coral reefs attract tourists to island, many of which are
impoverished and provide revenue.
 Reefs provide a barrier to prevent erosion and protect
from storms and floods.
 Provided millions of dollars worth of services

4. What is Coral Bleaching?
 Coral reefs get their bright colors from a mutualistic
relationship with algae called zooxanthellae.
 Zooxanthellae live in the coral and receive shelter and
compounds needed for photosythesis.
 Corals receive food from the zooxanthellae’s
photosynthesis products.
 this allows coral to secret calcium carbonate and grow.

5. What is Coral Bleaching?
 The tropical waters that corals grow in are very
nutrient poor.
 During photosynthesis the algae make oxygen. Corals
use oxygen to remove wastes.
 Zooxanthellea also provide the coral with glucose,
glycerol, and amino acids.

6. What is Coral bleaching?
 When the coral is under
stress it will expel it’s
zooxanthellae.
 This makes the coral
appear “bleached”
 The coral can no longer
build its calcium carbonate
skeleton.
 Can regain zooxanthellae if
stress is reduced. If not,
corals can die.

7. Coral Stressors
 What causes coral to expel the zooxanthellea?
 Rising water temperatures
 Pollution
 Overfishing
 Natural disasters
 Predation
 Coral mining
 Coral reefs are very fragile habitats.

8. Pollution and Natural Disasters
 The zooxanthellea need light from the sun for
photosynthesis.
 If pollution causes the water to be cloudy the sunlight
cannot reach the zooxanthellea and they cannot
produce the byproducts the coral depend on.
 Natural disasters can also cause the water to become
cloudy with sediment and block the sunlight.
 Natural disasters can also tear coral reefs apart and
extreme low tides can cause them to dry out and die.

9. Increased Carbon Dioxide
 A study was done (Hii et al. 2009) that tested the effect
of increased co2 on two different species of coral.
 Porites cylindrica and Galaxea fascicularis
 The increased C02 caused stress and reduced
zooxanthellae in both species of coral and caused
bleaching.
 Degree of stress was species dependent.

10. Temperature and Predation
 Corals live in a narrow temperature margin.
 A rise in temperature in 1-2 degrees for 5-10 weeks can
cause bleaching.
 Corals are also venerable to predation from starfish,
fish, crabs, worms, and snails.
 1978-1979 outbreak of crown-of-thorns starfish.

11. Coral mining and Overfishing
 The most devastating threat to corals come from
humans.
 Many coral reefs are harvested for aquarium fish and
decoration, jewelry, or building materials.
 Certain fishing techniques also kill coral.
 Blast fishing
 Cyanide fishing
 Deep water trawling

12. Areas of Mass Coral Bleaching

13. Coral Evolution
 The coral expelling their zooxanthellae may be an
adaptation so they can acquire different zooxanthellae
that can withstand the environmental stress.
 Some studies have shown an increased tolerance in
certain coral species (Maynard et al. 2008) when
comparing the damage from a bleaching event in 1998
and a bleaching event in 2002.
 Another study (McClanahan et al 2007) showed that
some corals seem to have acclimated to rising
temperature and bleach less, though these areas are
less diverse.

14. Coral Evolution
 The future of coral reefs will highly depend on how
quickly and efficiently they can adapt to global
changes.
 Although some coral species appear to be evolving a
tolerance for higher temperatures and Co2 levels,
human interference in reefs by harvesting and fishing
still pose a problem.

15. Protecting Coral Reefs
 In 1998 the United States established the Coral Reef
Task Force (CRTF) to protect and conserve coral reefs.
 The CRTF monitors and maps US coral reefs and
researches causes of coral bleaching. They also work
on finding ways to prevent bleaching.
 To fully protect reefs legal action may be needed such
as Marine Protected Areas.

16. Works Cited
 Buchheim Jason. Coral Reef Bleaching. 1998.
http://www.marinebiology.org/coralbleaching.htm. April 2010.
 Maynard, J. A., Anthony, K. R. N., Marshall, P. A. Masiri, I. 2008. Major bleaching events
can lead to increased thermal tolerance in corals. Marine Biology 155: 173-182.
 McClanahan, T. T., Ateweberhan, M., Muhando, C. A., Maina, J., Mohammed. M. S. 2007.
Effects of climate and seawater temperature variation on coral bleaching and mortality.
Ecological Monographs 77: 503-525.
 National Oceanic and Atmospheric Administration. March 25,2008
http://oceanservice.noaa.gov/education/kits/corals/coral11_protecting.html. April 2010.
 Yii-Siang Hii, Abol Munafi Ambok Bolong, Teng-Teng Yang, and Hock-Chark Liew,
“Effect of Elevated Carbon Dioxide on Two Scleractinian Corals: Porites cylindrica (Dana,
1846) and Galaxea fascicularis (Linnaeus, 1767),” Journal of Marine Biology, vol. 2009,
Article ID 215196, 7 pages, 2009.