Bleaching 'Devastates' Chagos Marine Reserve - BBC News

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bbc.com

Bleaching 'devastates' Chagos MarineReserve - BBC News

By Jonathan Amos BBC Science Correspondent

Image copyright Dan Bayley

Image caption Absent of colour: The anomalously warm temperatures have

persisted for months

The UK's largest tropical reef has been devastated in the global

bleaching event now under way.

Up to 85% of the corals in the Chagos Marine Reserve of the

British Indian Ocean Territory are estimated to have been damagedor killed in the event.

aching 'devastates' Chagos Marine Reserve - BBC News about:reader?url=http://www.bbc.com/news/science-environment-364...

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Scientists say the conditions there are worse than in 1998 - the last

major bleaching occurrence.

The problem is caused by anomalously warm water, which prompts

the coral polyps to eject their symbiotic algae.

This drains them of their colour and is fatal unless conditions are

reversed in a reasonably short time.

Unfortunately for the Chagos, the water has been persistently warm

for many months.

Image copyright Dan Bayley

Image caption The hope is that the juveniles will re-invade the reef from

deeper, cooler waters

"In 1998, the temperature that killed all the corals was probably

about 29.5C. Last year, in April, at the beginning of the latest

bleaching event, it was 30.5C and down to 25m. And this year scientists have been out and it's the same again," said Prof Charles

Sheppard, the chair of the Chagos Conservation Trust.

Prof Heather Koldewey, from the Zoological Society of London and

a CCT Trustee, led the expedition. She described what she saw as

shocking: "I was there two years ago and it's always an absolute joyto go diving in Chagos because you really get to see what a reef

should look like - rich, living corals with abundant fish and other


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marine life at densities you just don't get in other places. This was

very depressing."

Bleaching is happening globally on a huge scale because of the El

Nino phenomenon, which sees surface water temperatures spike inmany ocean regions.

Reports in the past couple of weeks have highlighted the damage

to the famous reefs off Australia and the Maldives.

The big question now is how well Chagos will recover when

conditions calm down, which they should do as the El Nino

subsides.

The reserve successfully bounced back after 1998, principally say

the scientists because it is normally such a pristine environment.

Image copyright NASA

Image caption Diego Garcia, which hosts a large US military base, is part

of the archipelago

Controversially, the Chagos Archipelago has been maintained


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relatively population free since the late 1960s, but this has had the

effect of limiting the stress factors that can weaken corals.

"This is what makes Chagos such an important reference site for

corals worldwide," explained Prof Koldewey.

"This is not an oil spill, this is not coastal pollution, sewage, or

overfishing or siltation. If anywhere can bounce back, it is the

Chagos Archipelago, and I hold on to that positive point of view."

Prof Sheppard said the hope would be that juveniles in deeper,

cooler water will come up to re-invade the reef and re-establish

communities.

The Chagos Marine Reserve was established in 2010 and covers

an area of 640,000 square kilometres - more than twice the area of

the UK.

The zone covered by reef is estimated to be about 60,000-80,000

square km.

Biodiversity catalogued in the reserve includes - in addition to the

corals - more than 1,000 species of fish; endangered green and

hawksbill turtles; the world's biggest land crab, the metre-spanningcoconut crab; and breeding colonies of terns and shearwaters.

[email protected] and follow me on Twitter:

@BBCAmos


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Bleaching 'Devastates' Chagos Marine Reserve - BBC News

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