Transcript Coral Bleaching

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,
chemicals, and other
resources .
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
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.
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.
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.
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.
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.
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.
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.
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
Areas of Mass Coral Bleaching
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.
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.
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.
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.