New deep sea habitat discovered in Irish waters

Limid bivalves Acesta excavata (red flesh) and deep-water oysters Neopycnodonte zibrowii dominate, together with the corals Madrepora oculata (lower centre, with branching shape) and Desmophyllum dianthus (solitary corals, for example lower left). Red dots produced by laser sightings are 10cm apart. Photo: NUI Galway.

Limid bivalves Acesta excavata (red flesh) and deep-water oysters Neopycnodonte zibrowii dominate, together with the corals Madrepora oculata (lower centre, with branching shape) and Desmophyllum dianthus (solitary corals, for example lower left). Red dots produced by laser sightings are 10cm apart. Photo: NUI Galway.

Marine researchers at NUI Galway have discovered a new habitat half a mile under the sea off Ireland’s southwest coast.

A team from the university’s Ryan Institute exploring the Whittard Canyon using the deep-water remotely operated vehicle ROV Holland I discovered a 150m vertical rock face in the canyon, which is rich in species of bivalves and corals. Some of the bivalves may be up to 200 years old.

“It is really unusual to see so many conspicuous animals so close together at these depths,” said Mark Johnson, Professor of Marine Environment at NUI Galway. “The bivalves are also remarkably large, and we know that deep-water oysters of this size elsewhere in European seas may be more than 200 years old. So we are probably seeing an exceptionally long-lived and stable community.”

Both bivalve shellfish and corals are filter feeders which generally feed on particles from surface waters. The team examined the area to determine how such a large community of animals were able to access sufficient food.

“We were particularly intrigued as to how food particles might be concentrated into one particular area and we found evidence for an internal wave caused by the shape of the canyon, which could be delivering food to the foot of the wall,” explained NUI Galway oceanographer Dr Martin White.

The Whittard Canyon system spans Irish, UK and French waters along the Atlantic margin. The survey took place in the Irish portion of the canyon.

“This habitat, because of its age and fragile structure is potentially extremely vulnerable to damage,” said NUI Galway zoologist Dr Louise Allcock, who led the team. “We need to establish where else it occurs and what measures are needed to protect it.”

The findings of the expedition have been published in the international academic journal PLOS ONE.

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