Coral Reef Deaths Soar in Record Ocean Heat
Coral reefs suffer mass bleaching
Coral reefs are
suffering widespread damage in what is set to be one of the worst years
ever for the delicate and beautiful habitats
The Telegraph (U.K.), July 19, 2010
Divers and
scientists have described huge areas of previously pristine reef being
turned into barren white undersea landscapes off the coast of Thailand
and Indonesia.
The popular
island tourist destination the Maldives have also suffered severe
bleaching. Reefs in the Caribbean could also be under threat.
High ocean
temperatures this year are being blamed for the bleaching, which experts
fear could be worse than a similar event in 1998 which saw an estimated
16 per cent of the world's reefs being destroyed.
Dr Mark Eakin,
coordinator of the National Oceanic and Atmospheric Administration's
Coral Reef Watch, said: "The bleaching is very strong throughout south
east Asia and the central Indian Ocean.
"The reports are
that it is the worst since 1997/1998. This is a really huge event and we
are going to see a lot of corals dying."
Coral reefs
provide refuge and food to nearly a quarter of all marine species,
making them among the most biologically diverse habitats on the planet.
Bleaching can also rob fish and other species of important shelter and
food sources.
Although reefs
can often recover from bleaching, it leaves the coral vulnerable to
damage from storms, infections and other environmental stress,
increasing the risk of deaths.
Coral reef
monitoring teams have reported mass bleaching of coral reefs off the
coast of Thailand, Malaysia, Vietnam, Cambodia and Indonesia while the
Maldives, Sri Lanka and reefs off the coast of east Africa have also
been hit.
With ocean
temperatures reaching record levels and combined with the end of an El
Nino episode, scientists fear there could be even more damage to corals
as the year continues.
Scientists in Thailand have reported reefs suffering 90% of their corals being bleached and up to 20% of the corals dead.
Olivia Durkin,
who is leading the bleaching monitoring at the Centre for Biodiversity
in Peninsular Thailand, said: "This year's severe coral bleaching has
the potential to be the worst on record.
"Extensive
bleaching, death and disease are reported not only in corals, but giant
clams, sea anemones and soft corals are also losing their symbiotic
algae."
Corals are a
delicate combination of animal, algae and rock that form intricate
undersea structures, providing shelter for thousands of brightly
coloured fish and also acting as nurseries for the young of many larger
open sea fish.
Coral colonies
are made up of polyps, which secrete a stony skeleton that forms the
intricate and delicate looking structures. A microscopic algae known as
zooxanthellae live within the coral where they convert energy from the
sun into food for the coral animals.
Bleaching usually
occurs when ocean temperatures exceed a threshold that is around one
degree higher than the average seen during the warmest summer months.
Although
scientists do not fully understand why it happens, bleaching is thought
to occur when these prolonged periods of these high temperatures combine
with excessive sunlight levels.
This causes the
symbiotic algae in the coral to become over active, causing it to poison
the coral host and leading to the coral expelling the algae into the
surrounding water to defend itself.
Without the algae
to provide food and nutrition, the corals grow weak and leaves them
vulnerable to disease and damage from storms.
In many cases the
coral dies, leaving an undersea wasteland that quickly becomes infested
with weedlike algae which covers every surface.
It can take
corals between 10 and 70 years to recover from such bleaching events.
Climate scientists have also warned that bleaching will become more
common as global temperatures continue to rise.
Research
published on Friday in the journal Science showed that coral growth in
the Red Sea has declined by a third over the past 12 years due to rising
temperatures and warned that coral there would cease growing entirely
by 2070 if warming continues.
Volunteers in
Cambodia say this year they have seen bleaching of 90% to 100% of the
shallow water reefs around the country's coast Koh Rong and Koh rong
Semleon Islands after water temperatures rose by 3 degrees.
Half of the reefs off Weh, in Indonesia have seen 80% of their corals bleached.
Stuart Campbell,
director of marines programs at the Wildlife Conservation Society in
Indonesia, said: "This is an unfortunate situation, as coral reefs of
northern Aceh have shown remarkable resilience in the aftermath of the
tsunami which hit the area in December 2004.
"In May 4% of colonies were recorded dead. The level of coral mortality that will occur in all is still unknown."
Many of the reefs in the Pacific that have been hit had survived previous bleaching events with little impact.
The reefs at Lord
Howe Island about 370 miles off the east coast of Australia. which are a
World Heritage Site for their unique beauty and biodiversity, have also
been hit by its largest ever recorded bleaching event.
Reefs in the
Maldives have been slowly recovering since high ocean temperatures in
1998 caused widespread bleaching of corals around the world. Biologists
fear this new bleaching will damage the already vulnerable reef further.
Mayotte, which is off the coast of northern Madagascar, has suffered high levels of mortality in the wake of the bleaching.
There are also
concerns that the bleaching could spread to popular tourist reefs in the
Caribbean after temperatures there have been high since the start of
the year.
Dr Eakin added: "This year may be a tough year in the Caribbean. It all depends on what the tropical storms do.
"When I visited
Thailand a couple of weeks ago, it was an eerie experience to look
around to see white in places that should have been full of bright
colours and life. It was almost worse than looking at a dead reef,
because what we were looking at was a reef that was right on the verge
of dying."
"It doesn't just
effect the corals themselves but the fish that live there. There were
anemone fish sitting in the middle of bleached anemone behaving
strangely and not defending their territory. It was like they were a
little stunned.
"For species that feed on coral, this is even worse for them."
There are also
concerns for the health of native UK corals growing off the coast after
species such as the pink sea fan have been devastated by disease.
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