Lophelia pertusa in the Atlantic Frontier

Lophelia pertusa and its similarity to tropical coral reefs

Lophelia pertusa is a deep-water, branching, cold water coral.

There is very limited knowledge regarding the biology and ecology of L. pertusa. However, if you compare the known features of the L. pertusa and tropical coral reefs, the two types of habitat have numerous similarities.

Past research indicates that approximately 800 species have been recorded as being associated with L. pertusa in the North East Atlantic. This means that the Lophelia reef habitat has high bio-diversity, which is approximately the same or higher as that of shallow reefs. Biodiversity is the variety of animals and plants living within a habitat. In species-rich ecosystems, such as coral reefs and rain forests, the inter-relationships of these species are extremely complex. Biodiversity is important for complex ecological reasons and because many species may have yet unforeseen usefulness to humankind. This may be in the form of commercial value (i.e. fish), commercially useful products and in terms of the genetic material which all organisms contain.

The reasons why L. pertusa is so biologically diverse are thought to be as follows. The coral occurs in a relatively stable environment with limited fluctuations in conditions. It occurs in regions with intermediate productivity which is known to favour greater bio-diversity. Also the coral provides a number of different types of habitats, which means that it offers a number of different conditions which accommodate a broader array of marine organisms.

L. pertusa is also similar in structure to its shallow water counter-parts. It is composed of an outer stratum of living coral polyps which is about one metre thick. The inner portion of the reef is composed of dead and decaying coral. It forms a long-lasting and complex coral debris. It is also eroded by similar groups of marine organisms (known as bio-eroders).

L. pertusa is considered to be a reef-forming coral, capable of building large coral banks hundreds of metres in width that may project tens of metres from the seabed.

The location of Lophelia pertusa in the Atlantic Frontier

L. pertusa has been recorded from the North East Atlantic more frequently than anywhere else in the world. This area probably represents a favoured habitat for L. pertusa and may be regarded as being of global significance for the species. Studies and fishing records relating to L. pertusa in the Atlantic Frontier indicate that the coral reefs do coincide with the blocks of seabed which have been licensed for oil and gas exploration under the 17th Round.

Oil exploration impacts on L. pertusa

The Oslo and Paris Conventions on Pollution at Sea: Species and Habitat Workshop in February 1997, identified L. pertusa as an eco-system of particular importance which is diverse and very sensitive but that has poor recoverability and that is declining in extent, declining in quality, threatened and in need of action.

The coral is so fragile that even wave pressure can break off its branches. Therefore any physical contact with the coral from industrialisation in the region (e.g.: anchors, anchor ropes, machinery etc.) is likely to cause localised impacts.

L. pertusa's distribution and historic evidence indicates that the species favours oceanic water. The reason for this is uncertain but it indicates that the coral may be highly sensitive to water quality.

Previous studies of L. pertusa indicate that there is a strong negative correlation between increased sediment cover of the coral and a decrease in the abundance of associated species with the coral. This means that the coral and it's associated bio-diversity of marine organisms are sensitive to smothering and therefore suggests that sediment from oil operations (derived from sources such as drill cuttings and muds) will impact upon the coral habitat adversely. In addition, the maintenance of a sediment free surface for colonisation appears to be important to many shallow and deep-water corals.

The ability of L. pertusa to recover from impacts is uncertain. The details of the species reproduction and larval development are unknown. This means that scientists have little if any indication of this species dispersal capabilities in the natural environment. In addition, the coral's growth rate has been estimated at 4-5mm a year which is thought to be much slower than reefs found in shallow water. The coral is also thought to survive within a fine balance between growth and erosion and that therefore any process which enhances the erosion or decline in abundance of the coral may not be rectified by simultaneous growth.

There are a number of different by-products produced during appraisal and production of oil that may impact upon L. pertusa.

Drill Cuttings - drilling in the Atlantic Frontier will involve the use of water based muds. These contain a variety of chemicals and are contaminated with toxic heavy metals. These will be released onto the seabed either directly or discharged from the platform. Toxins may reduce both species diversity and numbers. Sedimentation of corals is likely to reduce associated species diversity and impact coral growth. At worst, sedimentation will kill the coral.

Produced water which will be contaminated with injected chemicals and oil will be discharged.

Sand removed from the reserve which will contain a residue of oil will be released from the platform. Disposal of sand is likely to cause similar problems of sedimentation as mentioned above.

Drains are in place to channel contaminated water that overflows from collection trays under operating machinery.

Seabed Engineering - Sediment plumes will be created via the dragging and positioning of anchors and the construction/placement of well shoes and other submerged installations. There will also be localised impacts from mechanical damage to sessile and slow moving marine organisms.