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A Lophelia pertusa colony
Oil Affects on Reproduction of the Deep-Water Coral Lophelia pertusa on North Sea Oil Rigs
Waller, Roberts & Gass
The deep-sea coral Lophelia pertusa was first found growing on North Sea oil platforms in 1999, as the Brent Spar oil-storage buoy was decommissioned (Bell & Smith, 1999) and as the Beryl Alpha platform was surveyed (Pearce, 1999). This work showed corals were relatively abundant at depths beneath the seasonal thermocline in the northern North Sea (Roberts, 2002). The presence of deep-water corals within the NE Atlantic has been known for many years (Broch, 1922; Joubin, 1922; Dons, 1944; LeDanois, 1948; Zibrowius, 1980), but using new technologies, the true extent of the coral populations within European waters is just being appreciated (Mortensen et al., 1995; Henriet et al., 1998; Mortensen, 2000). The colonisation of L. pertusa on man made structures has been noted previously (Wilson, 1979) and so these oil rigs may be forming stepping stones in a larval supply route. L. pertusa is a cosmopolitan scleractinian, being found from depths of 50m in the Norwegian fjords (Hovland et al., 1998), to 3600m on the Mid-Atlantic Ridge (Bett et al., 1997) and in most of the worlds oceans. Deep-water reefs are now well recognised around the globe as important biomes for many fish and invertebrate species.
It has also been well documented that corals are particularly sensitive to anthropogenic impacts. There have been numerous reports of cold-water corals being adversely affected by deep-water trawling across the globe (Probert et al., 1997; Koslow & Gowlett-Jones, 1998; Freese et al., 1999; Bett, 2001; Brooke, 2002; Hall-Spencer, 2003; Waller & Tyler, in press; Wheeler et al., in press), yet the impact of oil platforms on the ecology of these organisms is unknown. Drill cuttings, produced water, drains, seabed engineering and sanitary waste would be the main input of poisonous chemicals into the benthic system close to oil production centres (Rogers, 1999). Drill cuttings are often laden with heavy metals and produced water may contain oil waste (Rogers, 1999) and benthic epifauna and infauna may also be smothered by these cuttings (Messieh et al., 1991). No studies have yet targeted oil pollution on deep-water corals, yet hydrocarbons have been shown to have detrimental affects on the reproduction of shallow-water species (Loya & Rinkevich, 1979; Guzman & Holst, 1993) and even on reproductive synchrony among colonies (Richmond, 1994). Growth may also be depressed (Birkeland et al., 1976) and even mass mortality may occur (Loya & Rinkevich, 1980; Brown, 1996). Oil pollution can remain for many years on shallow reef sites (Loya & Rinkevich, 1979; Brown, 1996) and so the affects can be long term (Loya, 1976). Differing species, however, show different responses to oil pollution (Brown, 1996), and so to correctly assess the effects of oil rigs on coral colonies it is important to assess these colonies directly. Bell and Smith (1999) argue that the position of these apparently healthy colonies negates against any detrimental affect caused by drilling. However, these corals may not, in fact, be subjected to any adverse conditions produced by the rigs, and may only colonise areas where the surrounding physical factors remove all pollutants (Roberts, 2000).
This project is in collaboration with researchers Murray Roberts and Susan Gass of the Scottish Association for Marine Science (Dunstaffnage Marine Laboratory). We are investigating the reproduction of colonies of Lophelia pertusa from different locations on oil rigs in the North Sea. This project mainly examines the effect of drilling fluids on these corals reproductive processes by studying colonies that have been collected from both exposed and unexposed areas of the drilling platforms. These samples have been collected during routine platform inspections by remotely operated vehicles (ROV) and we gratefully acknowledge the support of the members of the Atlantic Frontier Environmental Network and Subsea7.
There are four main objectives to be achieved by this project:
- To examine the gametogenesis and reproductive periodicity of Lophelia pertusa from the North Sea.
- To examine if reproductive and anatomical differences occur between Lophelia pertusa from areas likely to be exposed to drilling discharges, and colonies in unexposed or less exposed areas
- To use the data acquired to assess the general ‘health’ of Lophelia pertusa colonies growing on oil rigs in the North Sea.