‘Life on edge’: Irish cold water corals found thriving over 3,500m abyss

Cold-water coral grows at 750m in the Porcupine Bank Canyon. Photo: UCC Marine Geology Research Group

Lorna Siggins

Cold water corals can survive in extreme conditions within Ireland’s largest submarine canyon on the Porcupine Bank, a new study has found.

The coral even grows on precipices of high cliffs, and can withstand sea current speed of more than 114 centimetres per second, according to the study published today in science journal Nature.

This is the highest current speed ever recorded in a cold water habitat, according to University College Cork (UCC) scientist Dr Aaron Lim who led the research.

Dr Lim’s team used the Holland 1 remotely operated vehicle (ROV) on the State research ship Celtic Explorer to explore how coral are living in the 3.500m-deep Porcupine Bank Canyon.

He was part of the 2018 expedition which explored and mapped the canyon some 320km west of Kerry, finding it full of cold-water corals forming reefs and mounds which create a rim on the lip of the canyon.

This latest expedition found coral in a range of deep marine settings.

The scientists used deep-water monitoring stations and three-dimensional reconstructions in their work.

“These cold-water corals are growing at the very edge of a near-vertical cliff face, in Ireland’s largest submarine canyon some 850m below the surface in very intense conditions. They’re quite literally living on the edge,” Dr Lim said.

As he explained, cold-water corals help to form deep-water reefs and mounds which can range from as little as 10m to more than 100m high.

Some coral mounds have existed offshore Ireland for 2.6 million years, he said.

“Some of these habitats were predominantly alive, while others were mostly dead and so the aim of the study was to understand what is driving this,” explained Dr Lim.

UCC marine geologist Luke O’Reilly described the canyon as “a strange place; deep, dark and cold but full of life”. “Together with the Marine Institute, we developed a monitoring system which could withstand these pressures and conditions for months at a time,” he said.

Prof Andy Wheeler, head of UCC’s school of biological, earth and environmental sciences, noted the coral can cope with the strong sea currents, but tend to feed when it slows down – such as when the tide turns.

The team has recently deployed monitoring stations in the canyon to gather information on survival over longer time scales.

The research was funded by Science Foundation Ireland and Horizon 2020, with co-funding by the Marine Institute and Geological Survey, Ireland.