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Why the Coral Triangle is the most important part of the ocean

The Coral Triangle in Southeast Asia is the most diverse place in the ocean. And it could hold the secrets to protecting huge swathes of the planet's underwater habitats.

Dr Nadia Santodomingo, a coral expert at the Museum, is about to spend three years investigating the corals that live there.

Where is the Coral Triangle?

The Coral Triangle is a part of ocean spanning six million square kilometres, over Indonesia, Malaysia, Papua New Guinea, the Philippines, the Solomon Islands and Timor-Leste.

Although it's far less well-known than other places with abundant corals, like the Great Barrier Reef, the Coral Triangle is home to 30% of the world's reefs. In fact, when it comes to biodiversity, it is like nowhere else on Earth. More than 75% of the known coral species live there, as well as 37% of the world's coral reef fish.

It is home to six of the world's seven species of marine turtle, as well as blue whales, sperm whales, dolphins and dugongs.

Small blue fish swimming among clear water corals in Australia

Corals living in clear water off the coast of Australia. Nadia will study their counterparts living in muddier waters in the Coral Triangle in southeast Asia.


Nadia says, 'This part of the world contains the highest diversity of marine species. There are more than 600 reef species, which is ten times the number in the Caribbean Sea.

'Scientists have been trying to understand why it's so diverse for a very long time. Alfred Russell Wallace was working there when Darwin was alive, trying to get the bottom of the same problem.

'We need to understand this area fully if we are going to protect the rest of the world's oceans, especially the coral reefs. We need to know why so many species are thriving here, but not in other places.'

Crucially, many of the coral reefs that are blossoming in the area live in darker, muddier waters than their tropical counterparts, and it's these reefs that appear to be able to survive changing conditions and warming ocean temperatures.

The Natural Environment Research Council (NERC) has now given Nadia and an international team a grant to study these darker reefs.

Dr Nadia Santodomingo working in the field

Dr Nadia Santodomingo working in the field


Using fossils to predict the future of the Coral Triangle

To work out the reasons behind the Coral Triangle's success, researchers must search much further back in our planet's history.

Many scientists study the modern creatures that live in the area's vast reefs, but few have studied the fossils of the area.

Nadia previously worked with Museum palaeontologist Dr Ken Johnson on a large EU-funded project to collect fossils from eastern Borneo, very close to the Coral Triangle. Eight tonnes of samples were collected and are now stored in the Museum collections.

Palaeontologists found evidence of highly diverse marine life dating back 20 million years.

Ken says, 'In our previous research, we found that this area had very high biodiversity even 20 million years ago. To understand when life really began to bloom here, we need to go back even further in time, and that's one thing we hope to do in our upcoming project.'

By examining how and when corals in the Coral Triangle began to diversify, the team hope to figure out why the area continues to support so many animals and plants. They will also be able to work out how corals have responded to changing environmental conditions in the past. This includes times that were warmer than today, which might be comparable to future warm conditions.

Scientists will then have a better understanding of which other parts of the world may also do well in years to come, and which need greater protection.

Corals in the Museum collection

Corals in the Museum collection help to provide a baseline of biodiversity data


Corals on the margins

Plenty of coral reefs can be found in the world's clear blue, tropical waters, such as those around the Great Barrier Reef.

But there are plenty of other corals that live in darker and muddier areas of water, including in the Coral Triangle.

This part of Southeast Asia is mountainous, with volcanic activity and changeable weather conditions. This causes a lot of sediment to be disturbed in the water, blocking light to some of the reefs. Researchers suspect that these reefs, obscured by mud, are withstanding climate change far better than their relatives that live in clear, shallow waters.

Ken says, 'Nobody really thinks about these reefs, but they might be the ones we really want to protect. The corals living in more typical clear-water habitats have been hit hard by bleaching.

'Almost two thirds of the corals on the northern part of the Great Barrier Reef have been killed in the last few years.

'Corals living under continuous sediment stress seem to be more resilient, as the mud may block light, which in turn alleviates bleaching stress induced by high temperatures. The corals might also be able to change how they get their energy more easily.' 

Coral under a microscope

Coral under a microscope


Ken and Nadia also want to know whether the muddy-water and clear-water species can grow in each other's habitats. In other words, it's possible that the sturdier muddy corals could re-propagate the reefs that have been bleached.

It has been suggested that the muddy areas could be places where reef corals can retreat, persist in, and subsequently expand from, under changing environmental conditions.

Dr Natalie Cooper, a Museum researcher and expert on macroevolution, will help examine whether the coral species have been found in both habitats in the past.

By piecing together all this data and matching the fossils to their modern equivalents, the team hopes to be able to reconstruct the whole history of corals and reefs in the Coral Triangle.

Eventually, it is hoped this knowledge will inform conservation discussions of the future.