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An expedition to Christmas Island has found that this past year’s record El Niño has had a devastating effect on coral reefs near Christmas Island in the Pacific Ocean.

READ MORE: New images illustrate devastating coral bleaching in Australia’s Great Barrier Reef

Coral is actually an animal. The coral we see is made up of hundreds to thousands of small creatures called polyps which are extremely sensitive to temperatures. A warming of just 1 C to 1.5 C can cause the coral to undergo stress. Microscopic algae called zooxanthellae live inside the coral’s tissue and are responsible for providing coral with their colour. They also provide them with 90 per cent of the energy needed to grow as well as reproduce.

Coral bleaching off the coast of Christmas Island in the Pacific Ocean. Kristina Tietjen, UVic

Coral bleaching occurs when the relationship between the coral and the zooxanthellae breaks down, revealing the white “skeleton” of the host coral.

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The research team of marine scientists from the University of Victoria and the Georgia Institute of Technology visited Kiritimati Island, known best as Christmas Island, and were shocked to find how extreme the bleaching event was off the coast.

El Niño has caused ocean temperatures to rise in the Pacific Ocean, causing coral bleaching. Kristina Tietjen, UVic

Last November the team visited the reef and found that 50 to 90 per cent of the coral was bleached and as many as 30 per cent were dead. After returning in March, at least 80 per cent were dead and 15 per cent bleached.

GALLERY: Before and after photos of coral bleaching off Christmas Island

Coral bleaching in the Pacific Ocean near Christmas Island before El Niño. Kristina Tietjen, UVic Coral bleaching in the Pacific Ocean near Christmas Island after El Niño. Kristina Tietjen, UVic

“Christmas Island’s coral reefs are like ghost towns — the structures are all still there, but no one is home,” said University of Victoria biologist Julia Baum. “To see the reefs change this dramatically in just a few months is shocking.

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“We were bracing ourselves for the worst, but seeing it with our own eyes was surreal.” Tweet This

Over the past 10 months, temperatures on Christmas Island have been between 1.5 C and 3 C higher than normal.

Bleached coral in the Pacific Ocean, off the coast of Christmas Island. Kristina Tietjen, UVic

“This intense heat stress has transformed some of the world’s healthiest coral reefs into graveyards,” Baum said.

“To our knowledge, this is the greatest coral mass mortality event at a single location on record.” Tweet This

The effects of the bleaching extends beyond that of the ocean floor.

Bleached coral off the coast of Christmas Island. Kristina Tietjen, UVic

“Christmas Island’s people rely on the reefs for their food and their livelihoods, so they’ll be profoundly affected by this event,” Baum said.

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The team will continue to monitor the reef over the years to see how the reef recovers, which they say could take a decade or more.

In March, new video was released of the dramatic bleaching along Australia’s Great Barrier Reef. The Great Barrier Reef Marine Park Authority reported that 50 per cent of the coral deaths were due to sustained above-average sea surface temperatures.

WATCH: New footage of Great Barrier Reef’s coral bleaching

0:26 New footage of Great Barrier Reef’s coral bleaching New footage of Great Barrier Reef’s coral bleaching

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