Coral Bleaching

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Coral Bleaching

• Erica Weston

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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 .

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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

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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 zooxanthellaes
  photosynthesis products.
• this allows coral to secret calcium carbonate and
  grow.

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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.

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What is Coral bleaching?

• When the coral is under stress it will expel its
  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.

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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.

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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.

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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.

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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.

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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

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Areas of Mass Coral Bleaching
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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.

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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.

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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.

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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/educati
  on/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.