Protecting cold water corals that support an array of wildlife off our coasts
Lophelia pertusa is the great builder of deep-sea reefs, with live coral crests as rich in species as rainforests
Lophelia pertusa reef. Monitoring changes in reefs is prompting new remote video techniques, like that just pioneered by a science team from UCC. Illustration: Michael Viney
Lophelia pertusa has nothing to with Hamlet’s damsel in the river and is not, for that matter, even Latin. I was once dropped from a “bright” stream in school for my apparent lack of effort with that language, a lacuna (there you are) now sometimes regretted.
Curious about the meaning of the scientific name of a species, my quest is sometimes good for half a morning online. And while this name goes back, as so often, to Carl Linnaeus, who invented the two-name system of description using international Latin, Lophelia pertusa owes much to Greek.
The first word, it seems, blends lophos and helia to yield “a tuft of suns” – this for a deep-sea coral that lives in utter darkness. And pertusa, from the Latin, means “pierced with holes”, one way of seeing a colony of thousands of animals, each polyp fringed with 16 radiating tentacles, like a child’s drawing of a many-rayed sun.
Indeed, the polyps are often bright yellow, but can just as easily be creamy, pink or white. Rather than taking food from algae sheltering inside them, like the tropical corals near the ocean surface, they rely on snatching tiny organisms from passing currents or from the steady snowfall of particles from the busy life and death in sunlight far above.
Cold water corals
Lophelia pertusa is just one of the planet’s cold water corals, their number now some 3,300 species and climbing. But it is also the great builder of deep-sea reefs, notably in the northeast Atlantic. These hubs of marine life can be as big as small towns, rising up from the flatness of abyssal seabeds. Their live coral crests are intricately woven, as rich in species as rainforests. They are seen to attract the kinds of “commercial” fish that make up 90 per cent of the tonnage caught in the north Atlantic.
Irish and European scientific exploration was sparked in the 1990s by the sonar seabed maps of oil and gas exploration. It came just in time to discover the life of the deep coral reefs and to reveal its accelerating human destruction. Bottom trawling was already expanding along the continental shelf and delving ever deeper for new species.
A bycatch of metre-wide chunks of coral was hauled up and reefs rolled and smashed on both sides of the Atlantic. With some of the biggest reefs in the world, Norway was first to introduce protected zones of the kind followed by Ireland and the UK. The EU has also now banned bottom trawling deeper than 800m, which still leaves shallower reefs at risk.
Recovery of damaged coral is painfully slow, with natural regrowth measured in millimetres per year where possible at all. Monitoring changes in reefs is prompting new remote video techniques, like that just pioneered by a science team from University College Cork.
Using the Marine Institute’s van-sized undersea vehicle, ROV Holland 1, an overall mosaic of images focused on the whole surface of the Piddington Mound, an extensive reef on the Porcupine Seabight. At 1,000m down, this is one of the mounds in the protected “Belgica province” of elongated mounds near the edge of the shelf, southwest of Kerry. They are several million years old and sometimes more than 100m high.
Here, swept by strong currents rich in food supply, Lophelia pertusa is joined by Madrepora oculata, a coral species with elegantly zig-zagging branches. Earlier research assessed for the National Parks and Wildlife Service admired the “spectacular array” of species attached to the corals or living in their shelter, sponges, crustaceans, worms and shellfish among them.
Repeating their video survey after four years, the Cork team found unexpectedly strong bottom currents scouring the structure of Piddington Mound but leaving it with an unchanged share of living coral.
A recent study of the Darwin Mounds off the west coast of Scotland, after eight years of closure to fishing as a marine protected area, using ROV video, found protection had been successful for the western mounds, with unchanged proportions of live coral since their discovery in 1998. But the eastern mounds, severely damaged before the closure in 2011, showed no coral recolonisation and very little regrowth.
All European trawlers are now monitored by the mandatory fitting of VMS transmitters that beam their exact location, course and speed, every two hours, by way of satellite, to fishery authorities.
So VMS could indeed be working to keep reefs healthy, although the Scottish team found that “occasional violation still occurs”. In the system’s early days, there may have been temptation for trawler skippers to leave the VMS switched off , or even to find that machines were powering down all by themselves.
Such omissions seem to have been remedied. Norway, for example, insists that a trawler’s VMS stays on even in port, just to be sure where it is. Michael Viney’s Reflections on Another Life, a selection of columns from the past four decades, is available from irishtimes.com/irishtimesbooks; firstname.lastname@example.org