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The White-out Effect: Coral Bleaching
Coral reefs are exposed to numerous
natural and anthropogenic (human based)
threats. A few anthropogenic activities
that are harmful to corals include coastal
development, over fishing, oil discharge,
dumping of garbage, as well as, sedimentation
and pollution from agricultural
runoff. Some natural occurrences that
can also negatively affect coral reefs are
global climate change, coral bleaching,
hurricanes, and disease. Anthropogenic
activities have the potential to amplify the negative effects of natural occurrences
on coral reefs systems. One example of
this synergistic relationship is the increase
in greenhouse gases (GHG’s)
from industrial byproducts, their contribution
to global climate change, and coral
bleaching.
The rapid accumulation of GHG’s in
the atmosphere has already altered the
global climate. The average temperature
of the earth has increased 0.6°C to 0.8°C
in the past 100 years. By 2070, global climate models expect atmospheric temperatures
in the Caribbean region will
rise 2°C and 4°C. Since present sea surface
Bleaching causes coral to lose its
natural color and turn white. Hypotheses
exist that increases in sea surface
temperatures (SST) and hence,
climate change, is the most common
cause of bleaching over wide areas. |
temperatures (SST) are close to the
higher temperature levels for coral survival,
bleaching is predicted to become a
yearly event by 2020.
Bleaching happens when corals expel
their symbiotic algae called zooanthellae.
This causes coral to lose its natural color
and turn white. Bleaching can be a reaction
to a variety of stressors, such as
changes in salinity, excessive light, toxins,
and microbial infection. However, Continued on Page 15
hypotheses exist that increases in sea surface
temperatures (SST) and hence, climate
change, is the most common cause
of bleaching over wide areas. This is
because coral reefs are very sensitive
ecosystems, especially to changes in
water temperature above 30°C or below
22°C. Coral bleaching in the Caribbean
is often spurred by a rise of at least 1.0°C
in SST above normal summertime maximums
with duration of at least two or
three days.
Global Warming is believed to be the
chief cause of Coral Bleaching. |
Evidence suggests that the zooanthellae
present in corals can recover and regain
color within several months if the coral
bleaching event is not severe. Otherwise,
the coral dies. Multiple bleaching events
in the Caribbean over the last several decades
have resulted in widespread damage
to reef-building corals and thus, decline
in reef condition. According to the
Status of Coral Reefs of the World: 2004
Volume One, the reefs of Belize began
suffering from coral bleaching in June
and August of 1994. Acropora was the
species most affected. There has been a
50% coral reduction in live coral cover
in Belize between 1997 and 1999, and
cover has stayed relatively stable at that
level with slow recovery.
Many scientists agree that corals’ ability
to adapt to the environmental effects
resulting from climate change depends
on the severity of other human stresses
such as coastal development, over fishing,
oil discharge, dumping of wastes,
and pollution. A potentially effective management
tool that Belize utilizes in reducing
these stresses is marine protected
areas (MPAs’).
For more information on Green Reef please contact us at (email: [email protected] or telephone us at 226-2833.
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