Cold-water coral reef found in Irish waters is deepest yet

Scientists on board ‘Granuaile’ identify reef habitats at depths of 1,600m

The ‘Solenosmilia variabilis’ deep sea coral filmed at depths of 1,600 metres at the Porcupine Bank on the fringes of the Atlantic Ocean. Photograph: Marine Institute

Scientists have identified the deepest-known cold water coral reef in Irish waters during an expedition along the Porcupine Bank and Continental Shelf.

The reef, known as "Solenosmilia variabilis", was filmed at depths of 1,600 metres as part of a multiagency mapping project on board the Irish Lights ship Granuaile.

Scientists with the Marine Institute and National Parks and Wildlife Service (NPWS) were gathering data for marine planning, habitat protection and climate change impact measurement when they came across the reefs.

The “SeaRover” survey, as it is known, deployed the Marine Institute’s remotely operated vehicle (ROV) Holland 1, which is fitted with high-definition camera and lighting equipment and can work to depths of 3km.


“Some of the reef ecosystems and habitats we discovered have never been seen before, and discovering ‘Solenosmilia variabilis’ at depths greater than 1,600m helps us establish a better understanding of the environmental conditions necessary for this species to thrive,” chief scientist David O’Sullivan said.


This particular type of coral is normally seen at depths of between 1,000m to 1,300m on seamounts or rocky areas, he said, but only occasionally forms reefs.

“Its growth rate is very slow – approximately 1mm per year – so finding the reef structure, which is part of a fragile ecosystem thousands of years old, in deeper parts of the ocean is an important find for marine science,” he said.

The expedition team also identified a type of soft coral known as “sea pens”, which resemble a cross between a feather, starfish and fern.

"We have seen a wide variety of forms on this survey and can only give species names to very few, as many are likely to be new to science and have yet to be described," Dr Yvonne Leahy of the NPWS said.

The project is co-managed by the Integrated Mapping for the Sustainable Development of Ireland’s Marine Resources (INFOMAR) programme and fisheries science and ecosystem services at the Marine Institute and NPWS.

Lorna Siggins

Lorna Siggins

Lorna Siggins is the former western and marine correspondent of The Irish Times