Posted on 15.03.2006 - 01:52 EST in SCIENCE & TECH NEWS by Rons_ROV_Links
Oil and gas platforms abandoned at the end of their lives have become a breeding ground for marine wildlife, says Roger Highfield.
The platform stands as tall as the Canary Wharf tower and has reached the end of its working life in the North Sea. But rather than being yesterday's eyesore and bane of the environment, this hulking structure could be tomorrow's ecological darling.
Since the late 1940s, thousands of rigs have been planted in the world's shallow seas, with around 300 offshore installations in the unforgiving waters around the UK. Over the past decade, however, evidence has emerged that they are habitat forming.
Among those studied by marine scientists is BP's vast North West Hutton platform, which started to produce oil and gas more than two decades ago and has now reached the end of its life.
A convention has ruled that these structures must be completely removed. But this particular platform is so huge - standing 240 metres tall in 140 metres of water - that an exemption can be applied for and BP hopes (a Government decision is expected soon) to spend £160 million to remove most of the platform.
The remains of this 40,000-ton structure will provide the first artificial reef of its kind in the North Sea, an oasis on the sea bed, where life is relatively sparse.
Perhaps the most remarkable inhabitants of the platforms are corals, which most people associate with well lit, clear blue tropical waters, not the turbid waters in permanently dark waters deep in the north-east Atlantic. The commonest is Lophelia pertusa.
Like other corals, they consist of tiny animals - polyps - that use their tentacles to catch food particles floating in the water and, unlike their tropical peers, do not rely on algae to harness sunlight for energy. They also produce calcium carbonate skeletons - which grow into the framework of the coral reefs.
Coral larvae need a hard surface where they can settle, creating a strong attachment point for a new colony. Most of the North Sea bed is unsuitable for reefs - the bottom is muddy and has few rocky areas. But the oil and gas platforms are ideal platforms for corals. In turn, the reefs provide critical habitats for a multitude of other aquatic animals.
This deep-water coral supports a diverse community of sponges, seamats (bryozoans), anemones, bristle worms, crustaceans - the list goes on. As they flourish, they provide food and hiding places for little fish, which in turn provide food for bigger fish, building a diverse and complex habitat.
Ironically, the role of the rigs in hosting coral was revealed when decommissioning the Brent Spar oil rig in 1999, the subject of a long battle between the industry and environmentalists. Europe adopted a policy of removing rigs, rather than toppling them to make artificial reefs as is done in the Gulf of Mexico, because of environmental concerns about the debris that is left.
Surprised workers spotted Lophelia pertusa colonies on the Brent Spar structure. No one expected this cold-water coral would turn up on oil rigs. "This was good for us, since the rig provided an accessible environment," said Susan Gass, who has been surveying the rigs with Dr Murray Roberts of the Scottish Association for Marine Science in Oban.