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what
is
Coral bleaching?
Coral bleaching is the
name given to an event where coral expel their symbiotic algae due to extreme stress, such as unusually
hot water. Death follows if the stress is extreme or prolonged.
Coral
n.
- A rocklike deposit consisting of the calcareous skeletons secreted by various anthozoans. Coral deposits often accumulate to form reefs or islands in warm seas.
- Any of numerous chiefly colonial marine polyps of the class Anthozoa that secrete such calcareous skeletons.
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Bleach
v. bleached, bleaching, bleaches
- To remove the colour from, as by means of chemical agents or sunlight.
- To make white or colourless.
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Bleaching of corals
can eventually
lead to
their
death......
Coral reefs have always been resilient
and adaptable. They withstand numerous pressures, such as
crown-of-thorns starfish, extremes of weather (like cyclones) and
human activity of various kinds. Now throughout the world they are
facing the serious problem of rising sea surface temperatures (SST),
which is the primary cause of coral bleaching.
| Corals
are animals that are usually coloured tan, green or blue due
to the presence of millions of microscopic plant cells within
their tissues.
In a wonderful symbiosis, these
tiny plants utilize sunlight and the coral animal's respired
CO2 to produce energy rich compounds that feed the
coral host and release oxygen.
However when seas get to warm,
the delicate symbiosis collapses, the brown plant cells are
ejected, the white skeleton becomes visible through the now
transparent animal tissues, and the coral slowly starves. |
Bleached corals
white and alive but starving.
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AIMS scientist Dr Terry Done
says that certain kinds of corals are adapted to higher SST, and these
corals could "take over" as the seas warm. But at the moment,
the potential rate of adaptation is not known and more research is
needed ti investigate this possibility.
The future of the Great
Barrier Reef, and other reefs around the world. may not be as gloomy as
recent forecasts have stated. Certainly, Dr Done believes that the
pressure placed on coral reefs by global warming is another good reason
to take climate change seriously. But he and other senior reef
scientists are not prepared to say that the reef is going to die. Steps
need to be taken now to ensure that whatever we do to protect the reef
is based firmly on a foundation of knowledge that can only be obtained
by careful and sustained observation and analysis.
For further
information about coral bleaching:
Dr Terry Done, Leading
Scientist, AIMS
Phone 07 4753 4344
Email: t.done@aims.gov.au
See also:
 Coral
bleaching index - current and
archival information covering the past several years
 CRC
Reef Research Centre -
Townsville
Great
Barrier Reef Marine Park Authority -
Townsville
NOAA
National environmental satellite data -
USA
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