KOROR STATE GOVERNMENT MARINE TOUR GUIDE ... - C3

3.6.2 Climate Change
What is coral bleaching?
Coral bleaching is the loss of zoothanthellae from corals under stressful environmental
conditions. Microscopic algae called zoothanthellae live within corals and a vital source
of food in the form of sugars through photosynthesis. Zoothanthellae also contain
pigments that give coral their color. While any stress can cause corals to bleach, high
water temperature has been the major cause of coral bleaching events worldwide in
recent decades. Zoothanthellae are ejected under stressful circumstances and without
them, corals dependent upon zoothanthellae will eventually die. In addition to hard
corals, soft corals, giant clams and jellyfish area also dependent on zoothanthellae and
experience declines during bleaching. In 1997-1998, a major bleaching event in Palau’s
waters and elsewhere in the world, raised concerns about the health of the reef. With
predictions that temperatures will continue to rise as a result of global warming, the
future of tropical coral reefs is causing worldwide concern.
Causes of global climate change
Global climate change is the result of many complex environmental factors, but a
principal cause is the increasing amount of greenhouse gases in the atmosphere as a
result of human activity. The most significant greenhouse gas is carbon dioxide, which
has increased in concentration by more than a third in the last 200 years due to burning
of fossil fuels, and deforestation. The concentration of other gases, such as methane
and nitrous oxide, and the ozone-depleting halocarbon gases have also greatly
increased over the same period. Greenhouse gases in the atmosphere warm the air by
trapping heat from the Sun that would otherwise radiate from Earth back towards space.
The warming that results is similar to that which occurs inside a greenhouse.
Pat Colin
Over the 20 th century, the average temperature of the Earth’s surface rose by 0.6
degrees Celsius. According to a recent international study, it is projected to rise by
another 1.4-5.8 0 C over the next 100 years. At the same time, average sea surface
temperatures have also increased, although at a slower rate. Even small changes in sea
surface temperature can have a dramatic effect on global climate change. These include
ocean circulation patterns, increased frequency of storm events, and rising sea levels
due to expansion of warmed oceanic water and loss of ice.
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