New research by scientists in Cork has discovered that deep water coral reefs off the coast of Ireland are changing at a dramatic rate.

The researchers are not clear what is causing the transformation, but climate change is one theory being probed.

Over the course of four years, a 20% change was noted and the scientists say if the trend continues the reefs will be entirely different in just two decades.

The alterations were identified by two sessions of underwater filming on an area of a 1,000m-deep reef around the Belgica Mound Province, more than 100km southwest of the coast of Kerry.

Significant changes were identified between the first session in 2011, which was the first time an entire deep-water coral reef like this was imaged, and the second in 2015.

Over the four years, researchers Dr Aaron Lim from the Marine Geology Research Group in UCC and Professor Andy Wheeler, Head of Geology at UCC, noticed much larger amounts of dead coral and coral rubble.

However, the live coral remained largely unchanged.

The researchers say the differences were not the result of live coral dying, but are more likely to be the result of strong currents exposing dead coral buried beneath older parts of the reef.

"Although the corals live in deep water, they are part of the ecosystem, they are part of fisheries, part of surface productivity," said Prof Wheeler.

"What happens down there also affects us, and also affects our livelihoods."

The team are not speculating at this point about what is causing the currents, but climate change is one possibility being considered.

"I can't comment on whether it is climate change directly causing this, but the currents appear to be increasing so I would speculate that it could be related to climatic changes. But I wouldn't say for certain that it is," Dr Lim said.

It is the first time that researchers have been able to offer an insight into how reefs of this size grow and their results have been published in the journal Marine Geology.

According to the researchers, because of favourable conditions for their growth, the Irish continental margin is one of the most prolific places on the planet for deep water coral mound development.

Around the Belgica Mound Province, for example, 50 giant coral mounds and 300 smaller coral reefs have accumulated over millions of years.

Some are as big as several kilometres long and 100m tall.

"When people hear the word 'coral', they normally think shallow, tropical seas and sunshine," said Dr Lim.

"This couldn't be further from the truth. In fact, over half the species of coral are cold, deep-water species and many of them can be found in Irish waters between water depths of 600 m and 1000m."

The team utilised the Holland 1 remotely operated vehicle which was deployed from the deck of the Irish Marine Institute's RV Celtic Explorer.

The next stage of the research will involve Dr Lim and Prof Wheeler carrying out a sizable project to monitor a range of coral habitats on the Irish Margin with the aim of understanding what is driving these habitats and what makes them change.

"The issue is that it is so difficult to image the deep ocean that we can only get bits of information from these reefs during an expedition," said Prof Wheeler.