Biodiversity & Conservation

Lophelia reefs provide hard substrata and a complex network of potential niches for colonization by a wide variety of marine species. Lophelia and other cold-water corals support diverse, species rich, communities (Rogers, 1999). The diversity of polychaetes, echinoderms and bryozoans recorded from Lophelia reefs is similar to that found on shallow water tropical coral reefs (Rogers, 1999). However, Scleractina (corals), Mollusca and Pisces (fish) have relatively low diversities compared to tropical reefs (see Rogers, 1999). The diversity of species associated with Lophelia pertusa reefs is higher than the surrounding sediment, suggesting that these reefs may create biodiversity hot spots (Anon, 1999iv).

Jensen & Frederiksen (1992) recorded only juveniles of many of the species recorded in Lophelia reefs, which suggested that the reefs may act as a nursery area for many species (Rogers, 1999). Fosså et al. (2002) suggested that reefs may function as centres for the spread of associated fauna but noted that few species have, as yet, been identified as obligate reef dwellers. Video footage showed dense aggregations of redfish (Sebastes spp.) over reefs in Norwegian waters, females of which were gravid in May -June (Fosså et al., 2002). They also cite information from long-line catches, which suggested that catches of Sebastes spp. may be six times higher on the reefs, and two- three times higher for ling and tusk. Anecdotal reports from fishermen in Norwegian waters suggested that reefs were attractive fishing places (Fosså et al., 2002), however, fishermen working with mobile bottom gear usually avoid areas of rough ground due to damage to fishing gear (Hall-Spencer et al., 2002). Recent developments in trawling, such as rockhopper gear have allowed rough ground such as reefs to be fished (see exploitation; Rogers, 1999; Fosså et al., 2002). Overall, very little is known about the importance of Lophelia reefs for fish or for the wider ecosystem of the deep sea (Koslow et al., 2001; Fosså et al., 2002).

Lophelia reefs are not exploited directly but occur in areas subject to deep sea fishing (Rogers, 1999; Fosså et al., 2002; Hall-Spencer et al., 2002). The decline of traditional fisheries (e.g. cod) has resulted in increased interest in deep-sea species since the late 1980s (Rogers, 1999). Reefs are considered to be good fishing places for net and long-line fisheries, and fishermen often set their gear as close as possible to reefs but not on them to avoid damaging their fishing gear. However, the development of larger vessels and more powerful trawls, e.g. rockhopper gear designed to operate on rough stony bottoms, has probably exposed the reefs to increased impacts from fishing (Fosså et al., 2002). For example, the fishery of the continental break targeted Greenland halibut, redfish, and saithe. The orange-roughy is another valuable deep-sea species associated with offshore banks, pinnacles and canyons with strong currents, which are favoured by Lophelia (Rogers, 1999). In the UK, monkfish is a major fishery in the vicinity of the Lophelia reefs around Rockall (Dr Jason Hall-Spencer, pers comm.). Major fisheries in the vicinity of the 'Darwin Mounds' include deep-water demersal trawls for blue ling, orange roughy with a by-catch of black scabbard fish, Portuguese dogfish and leaf-scale gulper shark, long-lining for hake and deep-water sharks, and semi-pelagic trawling for blue whiting and argentine (Gubbay et al., 2002).

The potential effects of deep-sea fishing on the seabed and deep-water coral reefs has become a major concern (Rogers, 1999; Fosså et al., 2002; Hall-Spencer et al., 2002; Grehan et al., 2003). Photographic evidence of the effects of trawling damage, long line or fixed net fisheries, and discards on Lophelia reefs is shown in Fosså et al. (2002); Hall-Spencer et al., (2002) and Fosså (2003).

Evidence of damage to their cold-water coral reefs prompted Norway to designate its most important Lophelia reefs as marine reserves recently and ban towed-gear fisheries from them (Johnston & Tasker, 2002). Similarly, both Australia and New Zealand have created a network of seamount protected areas (Grehan et al., 2003). Grehan et al. (2003) found no evidence of trawl related damage in five deep-water coral locations in the Irish Porcupine Seabight and the Rockall Trough and suggested that these sites should be subject to protection urgently, especially in the light of the expanding deep-water fishery for orange-roughy. The 'Darwin Mounds' in the Rockall Trough are probably the most intensively studied cold-water coral reef known in UK waters. The 'Darwin Mounds' have recently been proposed as the first offshore candidate Special Area of Conservation (Johnston & Tasker, 2002). An outline management plan for the 'Darwin Mounds' was proposed by Gubbay et al. (2002). Grehan et al. (2003) noted that deep-water corals: may provide spawning grounds and refugia for juvenile fish of commercial fish species;may be a major source or sink of carbonate;could potentially be a paleo-climate indicator for the study of global climate change;and may be a potential source of novel pharmaceutical compounds. In addition, Hall-Spencer et al. (2002) noted that although all shallow water organisms had accumulated nuclear bomb test related 14C, the Lophelia specimens collected from deep-waters off west Ireland were not contaminated by anthropogenic 14C, presumably because the water bodies they occupy are ancient. Therefore, Lophelia at sites in west Ireland could provide a useful background or baseline level for studies of radioactive contamination.