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Coral Bleaching

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Erica Weston The Importance of Coral Reefs Coral reefs are like the rainforests of the sea Biologically diverse Support 33% of marine fish species Provides medicines ... – PowerPoint PPT presentation

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Title: Coral Bleaching


1
Coral Bleaching
  • 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 zooxanthellaes
    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 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.

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/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.
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