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Scope Series 4 RTÉ Two, Thursday, 7.00pm

Irish coral reefs

Andy WheelerWhen most people think of coral reefs they conjure up images of far-flung exotic destinations in the tropics. However, unbeknownst to many of us, Ireland’s chilly seas have been hiding vast and colourful living coral reefs for about two million years.

Ireland’s reefs grow during periods of relatively mild climate between ice ages, such as now. Forming enormous, hill-like mounds at depths of about 800 to 1,000 metres below the sea, these reefs are up to a kilometre wide and host a bevy of marine species including sponges, crabs, fish and shrimp.

The British Navy first dredged up live coral in 1869, so why are so many of us unaware of the emerald isle’s wealth of deep-sea life? Perhaps because only in the last decade or so has the technology existed to allow marine biologists and geologists to explore the reefs for themselves.

Using remotely operated vehicles weighing one tonne, scientists can virtually fly around the seabed, capturing images and live footage of the reefs. What they’ve discovered is that Ireland’s cold-water reefs are indeed as stunning and spectacular as their tropical counterparts.

CoralMarine biologist Andy Wheeler maps and studies the geology of these reefs. For Wheeler, exploring these reefs is a photogenic and charismatic science with the added bonus of getting to play with big and expensive toys.

What we typically picture as coral is actually a colony of many individual animals, known as coral polyps. Millions, or even billions, of these corals together form a reef.

Reefs are among the most diverse and productive communities on earth. They provide food and shelter for fish, eels and crustaceans and protect shores from erosion. In addition, scientists like Wheeler who study these reefs are able to learn about climate history. Certain corals are useful as fossils that geologists can use to date the age of the rocks in which they are found.

There are many different species of corals, each with a distinctive look and colour, which is what gives reefs their dazzling rainbow appearance. Corals feed mostly on microscopic plankton but larger varieties, including anemones, can feed on small fish. Corals usually grow in warm climates where there is clear salt water and sunlight, however, as with Ireland’s reefs, this is not always the case.

For example, the deep-water corals off the west coast of Ireland receive no sunlight. The common species that make up Irish reefs thrive in cold, dark waters as long as there’s enough of an ocean current to bring in food and oxygen.

Deep-water corals typically live between 200 to 2,000 metres in depth and some reefs are known to have grown up to 35 metres in height, hundreds of metres in width and up to 13 kilometres in length.

It is known that some of the coldwater reefs in Norway are up to 8,000 years old but the extent, age and biodiversity of living coral reefs in Ireland is still largely unknown.

 

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