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Coral Bleaching
Ann-Tin Cheng, ID#0628482
Cathy Wu, ID#0633019
Causes
Causes
1. Elevated/ Decreased Sea Water Temperature
2. Solar Irradiance
Regions
3. Subaerial Exposure
4. Sedimentation
Impacts
5. Fresh Water Dilution
6. Inorganic Nutrients
7.
Solution
Xenobiotics
8. Epizootics
9. Reduced Salinity
Conclusion
Causes
Regions
Impacts
Solution
Conclusion
Elevated/ Decreased Sea Water Temperature
Coral species live within a relatively narrow temperature margin,
and anomalously low and high sea temperatures can induce coral
bleaching. Bleaching events occur during sudden temperature
drops accompanying intense upwelling episodes, (-3 degrees
C to –5 degrees C for 5-10 days), seasonal cold-air outbreaks.
Bleaching is much more frequently reported from elevated se
water temperature. A small positive anomaly of 1-2 degrees C
for 5-10 weeks during the summer season will usually induce
bleaching.
Bleaching during the summer months, during seasonal
temperature and irradiance maxima often occurs
disproportionately in shallow-living corals and on the exposed
summits of colonies. Solar radiation has been suspected to play
a role in coral bleaching. Both photosyntheticaly active radiation
(PAR, 400-700nm) and ultraviolet radiation (UVR, 280-400nm)
have been implicated in bleaching.
Bleaching during the winter months may be a natural
phenomenon for high-latitude coral reefs. However, climnate
change may also lead to local decreases in temperature or to
greater variability in seasonal conditions. This could possibily
result in two consecutive bleaching events within one year of
the same reef. Cold water bleaching is therefore an additional
component to be considered among the climate change
projections for coral reefs at some locations.
Solar Irradiance
Bleaching during the summer months, during seasonal
temperature and irradiance maxima often occurs
disproportionately in shallow-living corals and on the exposed
summits of colonies. Solar radiation has been suspected to play
a role in coral bleaching. Both photosyntheticaly active radiation
(PAR, 400-700nm) and ultraviolet radiation (UVR, 280-400nm)
have been implicated in bleaching.
Subaerial Exposure
Sudden exposure of reef flat corals to the atmosphere during
events such as extreme low tides, ENSO-related sea level
drops or tectonic uplift can potentially induce bleaching. The
consequent exposure to high or low temperatures, increased
solar radiation, desiccation, and sea water dilution by heavy rains
could all play a role in zooxanthellae loss, but could also very well
lead to coral death.
Causes
Sedimentation
Relatively few instances of coral bleaching have been
linked solely to sediment. It is possible, but has not been
demonstrated, that sediment loading could make zooxanthellate
species more likely to bleach.
Fresh Water Dilution
Rapid dilution of reef waters from storm-generated precipitation
and runoff has been demonstrated to cause coral reef bleaching.
Generally, such bleaching events are rare and confined to
relatively small, nearshore areas.
Inorganic Nutrients
Rather than causing coral reef bleaching, an increase in ambient
elemental nutrient concentrations (e.g. ammonia and nitrate)
actually increases zooxanthellae densities 2-3 times. Although
eutrophication is not directly involved in zooxanthellae loss, it
could cause secondary adverse affects such as lowering of coral
resistance and greater susceptibility to diseases.
Xenobiotics
Zooxanthellae loss occurs during exposure of coral to elevated
concentrations of various chemical contaminants, such as Cu,
herbicides and oil. Because high concentrations of xenobiotics
are required to induce zooxanthellae loss, bleaching from such
sources is usually extremely localized and / or transitory .
Epizootics
Pathogen induced bleaching is different from other sorts of
bleaching. Most coral diseases cause patchy or whole colony
death and sloughing of soft tissues, resulting in a white skeleton
(not to be confused with bleached corals). A few pathogens have
been identified the cause translucent white tissues, a protozoan.
Reduced Salinity
This is a much more localised bleaching than the effects of
extensive sea temperature anomalies in the major tropical
oceans.
references:
Brown, B.. “Coral bleaching: causes and consequences.” Coral Reefs 161997 129-138. 23 Feb 2009
Dodge, Richard . “Low temperatures cause coral bleaching.” Coral Reefs 2329 July 2004 444. 23 Feb 2009
Causes
Regions
Impacts
Solution
Conclusion
Regions
Reef-base data of worldwide bleaching records (as of March 2008)
Causes
Regions
Regions
Mass coral moralities in coral reef ecosystems have been reported in all major reef provinces since the 1870s.
The frequency and scale of bleaching disturbances has increased dramatically since the late 70’s. This is
possibly due to more observers and a greater interest in reporting in recent years. More than 60 coral reef
bleaching events out of 105 mass coral moralities were reported between 1979-1990, compared with only
three bleaching events among 63 mass coral moralities recorded during the preceding 103 years.
Nearly all of the world’s major coral reef regions (Caribbean/ western Atlantic, eastern Pacific, central and
western Pacific, Indian Ocean, Arabian Gulf, Red Sea) experienced some degree of coral bleaching and
mortality during the 1980s.
Impacts
Solution
Prior to the 1980s, most mass coral moralities were related to non-thermal disturbances such as storms, aerial
exposures during extreme low tides, and Acanthaster outbreaks. Coral bleaching accompanied some of the
mortality events prior to the 1980s during periods of elevated sea water temperature, but these disturbances
were geographically isolated and restricted to particular reefs zones. In contrast, many of the coral bleaching
events observed in the 1980s occurred over large geographic regions and at all depths.
Most of the coral reef bleaching events of the 1980s occurred during years of large-scale ENSO activity.
Conclusion
In 1998, the worst coral bleaching in 700 years struck the Great Barrier Reef, followed by an even worse
bleaching only 4 years later. Massive areas of corals were affected all over the world. In Australia alone, the
2002 bleaching saw nearly 60 per cent of the reef suffer bleaching and, in the worst areas, 90% of the coral
was bleached. Aerial surveys of more than 640 reefs found that nearly 55% of the reef area in the Great
Barrier Reef Marine Park showed some degree of bleaching as a result of heat-stress. Not all reefs bleached
as severely as others and the impacts of bleaching were not evenly distributed throughout the Great Barrier
Reef.
The coral bleaching event in 2002 event was considered worse than the 1998 event because more reef area
was affected. The most severe bleaching occurred on reefs closest to shore in both bleaching events, but the
2002 event affected a greater area of reefs further offshore.
references:
Baker, Andre, Peter Glynn & Bernhard Riegl. “Climate change and coral reef bleaching: An ecological assessment of longterm impacts, recovery trends and future outlook.” Estuarine, Coastal and Shelf Science 802008 435-471. 23 Feb 2009
http://www.reef.crc.org.au/publications/brochures/2002event.htm
Impacts
Causes
Regions
Impacts
Solution
1
2
4
Conclusion
3
Impacts
Causes
Regions
Impacts
1.
Coral reefs generate billions of dollars in fishing and tourism. Tourism is the fastest growing
industry in the world, and coral reef tourism generates billions in areas such as Florida and
Australia, which would greatly affect these areas.
2.
Coral reefs protect coasts from strong currents and waves by providing a barrier that slows water
down before it reaches the shore. The costs of repairing damage from water currents are great and
definitely increase with the destruction of coral reefs.
3.
Globally, reefs generate about $30 billion annually in fishing, tourism, and protection to coasts from
storm surges.
4.
Coral are very important in controlling how much carbon dioxide is in the ocean water. Coral polyps
turn carbon dioxide in the water into a limestone shell. without coral, the amount of carbon dioxide
in the water would rise dramatically, and the acidity of the world’s oceans would increase and
threaten the future of our coral reef ecosystems.
5.
Coral reefs provide protection and shelter for many different species of fish. In terms of
biodiversity, coral reefs are often compared with tropical rain forests. Coral reefs shelter and
nourish up to 9 million species (a third of all known marine life forms) including 4000 kinds of fish.
Examples of animals that rely on coral reefs include parrotfish, butterflyfish, sponges, shrimp,
starfish, sea urchins, sea turtles, and many others.
Solution
Conclusion
SOURCES
http://oceanworld.tamu.edu/students/coral/coral4.htm
http://www.bios.edu/Labs/co2lab/research/Coral.html
http://www.usatoday.com/travel/destinations/2006-11-06-coral-reefs_x.htm
Solution
Causes
What is being done?
Regions
Impacts
Solution
Conclusion
1. by governments
• MPAs
• Biosphere reserves
• Marine parks and world
heritage sites
• Coral restoration methods
2. by people
• Adjust personal habits to be
more conscious of reefs
• Actively go out to help
coral reefs
Solution
Causes
1.
By governments
Implementation of Marine Protected Areas (MPAs). they are a lot like national parks and wildlife
refuges, in that potentially damaging extraction activies are prohibited. objectives are both social
and biological, including restoration of coral reefs, aesthetic maintenance, increased and protected
biodiversity, and economic benefits.
• Biosphere reserves are other protected areas that may protect reefs
• Marine parks and world heritage sites can provide protection for coral reefs.
• Low voltage electrical currents applied throuhg seawater crystallizes dissolved minerals onto steel
structures
• In large restoration projects, depending on type of coral, placement of propogated hermatype
coral through the use of metal pins are used. Also to restore large sections of broken coral reef,
concrete has also been used.
Special structures such as reef balls can be placed to provide corals a ground base to grow on.
•
Regions
Impacts
Solution
2.
•
Conclusion
•
By citizens
People who live near reefs are being encouraged toConserve water, use ecological or organic fertilizers, help reduce pollution, dispose of trash
properly, support reef-friendly businesses, dont touch reefs, practice safe/responsible diving and
snorkeling
Volunteer for coral reef cleanup, contact government representatives
SOURCES
http://www.nature.org/joinanddonate/rescuereef/explore/help.html
Causes
Regions
Impacts
Conclusion
• The most prominent reasons are sea water temperature change and solar
radiation.
• The most severe coral bleaching areas are: Caribbean/ western Atlantic and
western Pacific.
• Coral reefs impact: fishing, tourism, carbon dioxide levels in the ocean, and
the surrounding ocean biosphere
Other
Conclusion
• Both the government and everyday citizens are encouraged to do their part in
protecting coral reefs
Causes
Regions
Impacts
Solution
Conclusion
Conclusion
Coral reefs are important for many different reasons. Apart from protecting the shoreline from the
damaging effects of the ocean, they provide habitats and shelter for many organisms and are the
source of nitrogen and other nutrients essential for the food chain.
If a global warming trend impacts on shallow tropical and subtropical seas, we may expect an
increase in the frequency, severity and scale of coral reef bleaching. Coral mortality could exceed
95% regionally with species extirpation and extinctions. A conservative temperature increase of 1-2
degrees C would cause regions between 20-30 degrees N to experience sustained warming that
falls within the lethal limits of most reef-building coral species. In conjunction with sea temperature
rise would be a sea level rise, and it has been suggested that sea level rise would suppress coral
growth or kill many corals through drowning or lower light levels.
Some coral populations and their endosymbiotic zooxanthellae may be able to adapt to the extreme
conditions predicted during global climate change. Refuges in benign habitats, such as deep, sunlit
reef substrates, oceanic shoals and relatively high latitude locations, might exist, but widespread
coral mortality and reef decline would be expected in shallow reef zones in most low latitude.
Even if significant sea warming and elevated irradiance levels do not occur, coral reef degradation
from anthropogenic pollution and overexploitation will still continue, a result of unrelenting human
population growth.
Coral reefs impact the fishing and tourism industries, as well as provide protection to coastal
regions from storm surges. Furthermore, they are important in controlling the ocean’s carbon
dioxide levels and are home and shelter to a large part of the ocean biosphere that they are a part
of.
There are several ways people are trying to help damage to coral reefs. One way is through
government programs to protect and restore the reefs, and another way is by encouraging
everyday citizens who live near the reefs to adjust their daily habits to benefit the reefs, as well as
speak out and voice their support for protecting the reefs.